1
|
Tian M, Wang Z, Su Z, Shibata E, Shibata Y, Dutta A, Zang C. Integrative analysis of DNA replication origins and ORC-/MCM-binding sites in human cells reveals a lack of overlap. eLife 2024; 12:RP89548. [PMID: 38567819 PMCID: PMC10990492 DOI: 10.7554/elife.89548] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/05/2024] Open
Abstract
Based on experimentally determined average inter-origin distances of ~100 kb, DNA replication initiates from ~50,000 origins on human chromosomes in each cell cycle. The origins are believed to be specified by binding of factors like the origin recognition complex (ORC) or CTCF or other features like G-quadruplexes. We have performed an integrative analysis of 113 genome-wide human origin profiles (from five different techniques) and five ORC-binding profiles to critically evaluate whether the most reproducible origins are specified by these features. Out of ~7.5 million union origins identified by all datasets, only 0.27% (20,250 shared origins) were reproducibly obtained in at least 20 independent SNS-seq datasets and contained in initiation zones identified by each of three other techniques, suggesting extensive variability in origin usage and identification. Also, 21% of the shared origins overlap with transcriptional promoters, posing a conundrum. Although the shared origins overlap more than union origins with constitutive CTCF-binding sites, G-quadruplex sites, and activating histone marks, these overlaps are comparable or less than that of known transcription start sites, so that these features could be enriched in origins because of the overlap of origins with epigenetically open, promoter-like sequences. Only 6.4% of the 20,250 shared origins were within 1 kb from any of the ~13,000 reproducible ORC-binding sites in human cancer cells, and only 4.5% were within 1 kb of the ~11,000 union MCM2-7-binding sites in contrast to the nearly 100% overlap in the two comparisons in the yeast, Saccharomyces cerevisiae. Thus, in human cancer cell lines, replication origins appear to be specified by highly variable stochastic events dependent on the high epigenetic accessibility around promoters, without extensive overlap between the most reproducible origins and currently known ORC- or MCM-binding sites.
Collapse
Affiliation(s)
- Mengxue Tian
- Center for Public Health Genomics, University of Virginia School of MedicineCharlottesvilleUnited States
- Department of Biochemistry and Molecular Genetics, University of Virginia School of MedicineCharlottesvilleUnited States
| | - Zhenjia Wang
- Center for Public Health Genomics, University of Virginia School of MedicineCharlottesvilleUnited States
| | - Zhangli Su
- Department of Biochemistry and Molecular Genetics, University of Virginia School of MedicineCharlottesvilleUnited States
- Department of Genetics, University of Alabama at BirminghamBirminghamUnited States
| | - Etsuko Shibata
- Department of Biochemistry and Molecular Genetics, University of Virginia School of MedicineCharlottesvilleUnited States
- Department of Genetics, University of Alabama at BirminghamBirminghamUnited States
| | - Yoshiyuki Shibata
- Department of Biochemistry and Molecular Genetics, University of Virginia School of MedicineCharlottesvilleUnited States
- Department of Genetics, University of Alabama at BirminghamBirminghamUnited States
| | - Anindya Dutta
- Department of Biochemistry and Molecular Genetics, University of Virginia School of MedicineCharlottesvilleUnited States
- Department of Genetics, University of Alabama at BirminghamBirminghamUnited States
| | - Chongzhi Zang
- Center for Public Health Genomics, University of Virginia School of MedicineCharlottesvilleUnited States
- Department of Biochemistry and Molecular Genetics, University of Virginia School of MedicineCharlottesvilleUnited States
- Department of Public Health Sciences, University of VirginiaCharlottesvilleUnited States
| |
Collapse
|
2
|
Foss EJ, Lichauco C, Gatbonton-Schwager T, Gonske SJ, Lofts B, Lao U, Bedalov A. Identification of 1600 replication origins in S. cerevisiae. eLife 2024; 12:RP88087. [PMID: 38315095 PMCID: PMC10945306 DOI: 10.7554/elife.88087] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2024] Open
Abstract
There are approximately 500 known origins of replication in the yeast genome, and the process by which DNA replication initiates at these locations is well understood. In particular, these sites are made competent to initiate replication by loading of the Mcm replicative helicase prior to the start of S phase; thus, 'a site that binds Mcm in G1' might be considered to provide an operational definition of a replication origin. By fusing a subunit of Mcm to micrococcal nuclease, we previously showed that known origins are typically bound by a single Mcm double hexamer, loaded adjacent to the ARS consensus sequence (ACS). Here, we extend this analysis from known origins to the entire genome, identifying candidate Mcm binding sites whose signal intensity varies over at least three orders of magnitude. Published data quantifying single-stranded DNA (ssDNA) during S phase revealed replication initiation among the most abundant 1600 of these sites, with replication activity decreasing with Mcm abundance and disappearing at the limit of detection of ssDNA. Three other hallmarks of replication origins were apparent among the most abundant 5500 sites. Specifically, these sites: (1) appeared in intergenic nucleosome-free regions flanked on one or both sides by well-positioned nucleosomes; (2) were flanked by ACSs; and (3) exhibited a pattern of GC skew characteristic of replication initiation. We conclude that, if sites at which Mcm double hexamers are loaded can function as replication origins, then DNA replication origins are at least threefold more abundant than previously assumed, and we suggest that replication may occasionally initiate in essentially every intergenic region. These results shed light on recent reports that as many as 15% of replication events initiate outside of known origins, and this broader distribution of replication origins suggest that S phase in yeast may be less distinct from that in humans than widely assumed.
Collapse
Affiliation(s)
- Eric J Foss
- Clinical Research Division, Fred Hutch Cancer CenterSeattleUnited States
| | - Carmina Lichauco
- Clinical Research Division, Fred Hutch Cancer CenterSeattleUnited States
| | | | - Sara J Gonske
- Clinical Research Division, Fred Hutch Cancer CenterSeattleUnited States
| | - Brandon Lofts
- Clinical Research Division, Fred Hutch Cancer CenterSeattleUnited States
| | - Uyen Lao
- Clinical Research Division, Fred Hutch Cancer CenterSeattleUnited States
| | - Antonio Bedalov
- Clinical Research Division, Fred Hutch Cancer CenterSeattleUnited States
| |
Collapse
|
3
|
Tian M, Wang Z, Su Z, Shibata E, Shibata Y, Dutta A, Zang C. Integrative analysis of DNA replication origins and ORC/MCM binding sites in human cells reveals a lack of overlap. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.25.550556. [PMID: 37546918 PMCID: PMC10402023 DOI: 10.1101/2023.07.25.550556] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/08/2023]
Abstract
Based on experimentally determined average inter-origin distances of ∼100 kb, DNA replication initiates from ∼50,000 origins on human chromosomes in each cell cycle. The origins are believed to be specified by binding of factors like the Origin Recognition Complex (ORC) or CTCF or other features like G-quadruplexes. We have performed an integrative analysis of 113 genome-wide human origin profiles (from five different techniques) and 5 ORC-binding profiles to critically evaluate whether the most reproducible origins are specified by these features. Out of ∼7.5 million union origins identified by all datasets, only 0.27% were reproducibly obtained in at least 20 independent SNS-seq datasets and contained in initiation zones identified by each of three other techniques (20,250 shared origins), suggesting extensive variability in origin usage and identification. 21% of the shared origins overlap with transcriptional promoters, posing a conundrum. Although the shared origins overlap more than union origins with constitutive CTCF binding sites, G-quadruplex sites and activating histone marks, these overlaps are comparable or less than that of known Transcription Start Sites, so that these features could be enriched in origins because of the overlap of origins with epigenetically open, promoter-like sequences. Only 6.4% of the 20,250 shared origins were within 1 kb from any of the ∼13,000 reproducible ORC binding sites in human cancer cells, and only 4.5% were within 1 kb of the ∼11,000 union MCM2-7 binding sites in contrast to the nearly 100% overlap in the two comparisons in the yeast, S. cerevisiae . Thus, in human cancer cell lines, replication origins appear to be specified by highly variable stochastic events dependent on the high epigenetic accessibility around promoters, without extensive overlap between the most reproducible origins and currently known ORC- or MCM-binding sites.
Collapse
|
4
|
Foss EJ, Lichauco C, Gatbonton-Schwager T, Gonske SJ, Lofts B, Lao U, Bedalov A. Identification of 1600 replication origins in S. cerevisiae. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.04.11.536402. [PMID: 38014147 PMCID: PMC10680564 DOI: 10.1101/2023.04.11.536402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2023]
Abstract
There are approximately 500 known origins of replication in the yeast genome, and the process by which DNA replication initiates at these locations is well understood. In particular, these sites are made competent to initiate replication by loading of the Mcm replicative helicase prior to the start of S phase; thus, "a site to which MCM is bound in G1" might be considered to provide an operational definition of a replication origin. By fusing a subunit of Mcm to micrococcal nuclease, a technique referred to as "Chromatin Endogenous Cleavage", we previously showed that known origins are typically bound by a single Mcm double hexamer, loaded adjacent to the ARS consensus sequence (ACS). Here we extend this analysis from known origins to the entire genome, identifying candidate Mcm binding sites whose signal intensity varies over at least 3 orders of magnitude. Published data quantifying the production of ssDNA during S phase showed clear evidence of replication initiation among the most abundant 1600 of these sites, with replication activity decreasing in concert with Mcm abundance and disappearing at the limit of detection of ssDNA. Three other hallmarks of replication origins were apparent among the most abundant 5,500 sites. Specifically, these sites (1) appeared in intergenic nucleosome-free regions that were flanked on one or both sides by well-positioned nucleosomes; (2) were flanked by ACSs; and (3) exhibited a pattern of GC skew characteristic of replication initiation. Furthermore, the high resolution of this technique allowed us to demonstrate a strong bias for detecting Mcm double-hexamers downstream rather than upstream of the ACS, which is consistent with the directionality of Mcm loading by Orc that has been observed in vitro. We conclude that, if sites at which Mcm double-hexamers are loaded can function as replication origins, then DNA replication origins are at least 3-fold more abundant than previously assumed, and we suggest that replication may occasionally initiate in essentially every intergenic region. These results shed light on recent reports that as many as 15% of replication events initiate outside of known origins, and this broader distribution of replication origins suggest that S phase in yeast may be less distinct from that in humans than is widely assumed.
Collapse
Affiliation(s)
- Eric J Foss
- Clinical Research Division, Fred Hutch Cancer Center, Seattle, WA 98109
| | - Carmina Lichauco
- Clinical Research Division, Fred Hutch Cancer Center, Seattle, WA 98109
| | | | - Sara J Gonske
- Clinical Research Division, Fred Hutch Cancer Center, Seattle, WA 98109
| | - Brandon Lofts
- Clinical Research Division, Fred Hutch Cancer Center, Seattle, WA 98109
| | - Uyen Lao
- Clinical Research Division, Fred Hutch Cancer Center, Seattle, WA 98109
| | - Antonio Bedalov
- Clinical Research Division, Fred Hutch Cancer Center, Seattle, WA 98109
| |
Collapse
|
5
|
Laughery MF, Plummer DA, Wilson HE, Vandenberg BN, Mitchell D, Mieczkowski PA, Roberts SA, Wyrick JJ. Genome-wide maps of UVA and UVB mutagenesis in yeast reveal distinct causative lesions and mutational strand asymmetries. Genetics 2023; 224:iyad086. [PMID: 37170598 PMCID: PMC10324949 DOI: 10.1093/genetics/iyad086] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2023] [Revised: 05/01/2023] [Accepted: 05/03/2023] [Indexed: 05/13/2023] Open
Abstract
Ultraviolet (UV) light primarily causes C > T substitutions in lesion-forming dipyrimidine sequences. However, many of the key driver mutations in melanoma do not fit this canonical UV signature, but are instead caused by T > A, T > C, or C > A substitutions. To what extent exposure to the UVB or UVA spectrum of sunlight can induce these noncanonical mutation classes, and the molecular mechanism involved is unclear. Here, we repeatedly exposed wild-type or repair-deficient yeast (Saccharomyces cerevisiae) to UVB or UVA light and characterized the resulting mutations by whole genome sequencing. Our data indicate that UVB induces C > T and T > C substitutions in dipyrimidines, and T > A substitutions that are often associated with thymine-adenine (TA) sequences. All of these mutation classes are induced in nucleotide excision repair-deficient cells and show transcriptional strand asymmetry, suggesting they are caused by helix-distorting UV photoproducts. In contrast, UVA exposure induces orders of magnitude fewer mutations with a distinct mutation spectrum. UVA-induced mutations are elevated in Ogg1-deficient cells, and the resulting spectrum consists almost entirely of C > A/G > T mutations, indicating they are likely derived from oxidative guanine lesions. These mutations show replication asymmetry, with elevated G > T mutations on the leading strand, suggesting there is a strand bias in the removal or bypass of guanine lesions during replication. Finally, we develop a mutation reporter to show that UVA induces a G > T reversion mutation in yeast that mimics the oncogenic NRAS Q61K mutation in melanoma. Taken together, these findings indicate that UVA and UVB exposure can induce many of the noncanonical mutation classes that cause driver mutations in melanoma.
Collapse
Affiliation(s)
- Marian F Laughery
- School of Molecular Biosciences, Washington State University, Pullman, WA 99164, USA
| | - Dalton A Plummer
- School of Molecular Biosciences, Washington State University, Pullman, WA 99164, USA
| | - Hannah E Wilson
- School of Molecular Biosciences, Washington State University, Pullman, WA 99164, USA
| | - Brittany N Vandenberg
- School of Molecular Biosciences, Washington State University, Pullman, WA 99164, USA
| | - Debra Mitchell
- School of Molecular Biosciences, Washington State University, Pullman, WA 99164, USA
| | - Piotr A Mieczkowski
- Department of Genetics, Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Steven A Roberts
- School of Molecular Biosciences, Washington State University, Pullman, WA 99164, USA
- Center for Reproductive Biology, Washington State University, Pullman, WA 99164, USA
| | - John J Wyrick
- School of Molecular Biosciences, Washington State University, Pullman, WA 99164, USA
| |
Collapse
|
6
|
Petrie MV, He Y, Gan Y, Ostrow AZ, Aparicio OM. Broadly Applicable Control Approaches Improve Accuracy of ChIP-Seq Data. Int J Mol Sci 2023; 24:9271. [PMID: 37298223 PMCID: PMC10252487 DOI: 10.3390/ijms24119271] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2023] [Revised: 05/18/2023] [Accepted: 05/23/2023] [Indexed: 06/12/2023] Open
Abstract
Chromatin ImmunoPrecipitation (ChIP) is a widely used method for the analysis of protein-DNA interactions in vivo; however, ChIP has pitfalls, particularly false-positive signal enrichment that permeates the data. We have developed a new approach to control for non-specific enrichment in ChIP that involves the expression of a non-genome-binding protein targeted in the IP alongside the experimental target protein due to the sharing of epitope tags. ChIP of the protein provides a "sensor" for non-specific enrichment that can be used for the normalization of the experimental data, thereby correcting for non-specific signals and improving data quality as validated against known binding sites for several proteins that we tested, including Fkh1, Orc1, Mcm4, and Sir2. We also tested a DNA-binding mutant approach and showed that, when feasible, ChIP of a site-specific DNA-binding mutant of the target protein is likely an ideal control. These methods vastly improve our ChIP-seq results in S. cerevisiae and should be applicable in other systems.
Collapse
Affiliation(s)
| | | | | | | | - Oscar M. Aparicio
- Molecular and Computational Biology Section, University of Southern California, Los Angeles, CA 90089, USA; (M.V.P.); (Y.H.); (Y.G.); (A.Z.O.)
| |
Collapse
|
7
|
Kwan EX, Alvino GM, Lynch KL, Levan PF, Amemiya HM, Wang XS, Johnson SA, Sanchez JC, Miller MA, Croy M, Lee SB, Naushab M, Bedalov A, Cuperus JT, Brewer BJ, Queitsch C, Raghuraman MK. Ribosomal DNA replication time coordinates completion of genome replication and anaphase in yeast. Cell Rep 2023; 42:112161. [PMID: 36842087 PMCID: PMC10142053 DOI: 10.1016/j.celrep.2023.112161] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 12/19/2022] [Accepted: 02/09/2023] [Indexed: 02/27/2023] Open
Abstract
Timely completion of genome replication is a prerequisite for mitosis, genome integrity, and cell survival. A challenge to this timely completion comes from the need to replicate the hundreds of untranscribed copies of rDNA that organisms maintain in addition to the copies required for ribosome biogenesis. Replication of these rDNA arrays is relegated to late S phase despite their large size, repetitive nature, and essentiality. Here, we show that, in Saccharomyces cerevisiae, reducing the number of rDNA repeats leads to early rDNA replication, which results in delaying replication elsewhere in the genome. Moreover, cells with early-replicating rDNA arrays and delayed genome-wide replication aberrantly release the mitotic phosphatase Cdc14 from the nucleolus and enter anaphase prematurely. We propose that rDNA copy number determines the replication time of the rDNA locus and that the release of Cdc14 upon completion of rDNA replication is a signal for cell cycle progression.
Collapse
Affiliation(s)
- Elizabeth X Kwan
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
| | - Gina M Alvino
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
| | - Kelsey L Lynch
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
| | - Paula F Levan
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
| | - Haley M Amemiya
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
| | - Xiaobin S Wang
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
| | - Sarah A Johnson
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
| | - Joseph C Sanchez
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
| | - Madison A Miller
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
| | - Mackenzie Croy
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
| | - Seung-Been Lee
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
| | - Maria Naushab
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
| | - Antonio Bedalov
- Clinical Research Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
| | - Josh T Cuperus
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
| | - Bonita J Brewer
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
| | - Christine Queitsch
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA.
| | - M K Raghuraman
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA.
| |
Collapse
|
8
|
Dbf4 Zn-Finger Motif Is Specifically Required for Stimulation of Ctf19-Activated Origins in Saccharomyces cerevisiae. Genes (Basel) 2022; 13:genes13122202. [PMID: 36553469 PMCID: PMC9778208 DOI: 10.3390/genes13122202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2022] [Revised: 11/11/2022] [Accepted: 11/17/2022] [Indexed: 11/25/2022] Open
Abstract
Eukaryotic genomes are replicated in spatiotemporal patterns that are stereotypical for individual genomes and developmental profiles. In the model system Saccharomyces cerevisiae, two primary mechanisms determine the preferential activation of replication origins during early S phase, thereby largely defining the consequent replication profiles of these cells. Both mechanisms are thought to act through specific recruitment of a rate-limiting initiation factor, Dbf4-dependent kinase (DDK), to a subset of licensed replication origins. Fkh1/2 is responsible for stimulation of most early-firing origins, except for centromere (CEN)-proximal origins that recruit DDK via the kinetochore protein Ctf19, which is required for their early firing. The C-terminus of Dbf4 has been implicated in its recruitment to origins via both the Fkh1/2 and Ctf19 mechanisms. Here, we show that the Zn-finger motif within the C-terminus is specifically required for Dbf4 recruitment to CENs to stimulate CEN-proximal/Ctf19-dependent origins, whereas stimulation of origins via the Fkh1/2 pathway remains largely intact. These findings re-open the question of exactly how Fkh1/2 and DDK act together to stimulate replication origin initiation.
Collapse
|
9
|
Rpd3 regulates single-copy origins independently of the rDNA array by opposing Fkh1-mediated origin stimulation. Proc Natl Acad Sci U S A 2022; 119:e2212134119. [PMID: 36161938 PMCID: PMC9546531 DOI: 10.1073/pnas.2212134119] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022] Open
Abstract
The faithful replication of eukaryotic genomes requires balancing the replication capacities of different genomic regions, such as repetitive versus single-copy genetic elements, which may compete for limiting replication resources, possibly leading to replication stress and genome instability. We examined the function of histone deacetylases Rpd3 and Sir2 in balancing replication between unique genome sequences and the multicopy ribosomal DNA genes. Our findings support prior conclusions that Sir2 directly suppresses early firing of rDNA origins, thereby enabling balanced replication of the genome. We further show that Rpd3’s function in delaying firing of later-firing, single-copy origins is independent of Sir2 and rDNA load. Instead, Rpd3 appears to oppose the Fkh1/2 origin activation pathway by regulating binding of the origin-stimulator Fkh1. Eukaryotic chromosomes are organized into structural and functional domains with characteristic replication timings, which are thought to contribute to epigenetic programming and genome stability. Differential replication timing results from epigenetic mechanisms that positively and negatively regulate the competition for limiting replication initiation factors. Histone deacetylase Sir2 negatively regulates initiation of the multicopy (∼150) rDNA origins, while Rpd3 histone deacetylase negatively regulates firing of single-copy origins. However, Rpd3’s effect on single-copy origins might derive indirectly from a positive function for Rpd3 in rDNA origin firing shifting the competitive balance. Our quantitative experiments support the idea that origins compete for limiting factors; however, our results show that Rpd3’s effect on single-copy origin is independent of rDNA copy-number and of Sir2’s effects on rDNA origin firing. Whereas RPD3 deletion and SIR2 deletion alter the early S phase dynamics of single-copy and rDNA origin firings in opposite fashion, unexpectedly only RPD3 deletion suppresses overall rDNA origin efficiency across S phase. Increased origin activation in rpd3Δ requires Fkh1/2, suggesting that Rpd3 opposes Fkh1/2-origin stimulation, which involves recruitment of Dbf4-dependent kinase (DDK). Indeed, Fkh1 binding increases at Rpd3-regulated origins in rpd3Δ cells in G1, supporting a mechanism whereby Rpd3 influences initiation timing of single-copy origins directly through modulation of Fkh1-origin binding. Genetic suppression of a DBF4 hypomorphic mutation by RPD3 deletion further supports the conclusion that Rpd3 impedes DDK recruitment by Fkh1, revealing a mechanism of Rpd3 in origin regulation.
Collapse
|
10
|
Lazar-Stefanita L, Luo J, Montagne R, Thierry A, Sun X, Mercy G, Mozziconacci J, Koszul R, Boeke JD. Karyotype engineering reveals spatio-temporal control of replication firing and gene contacts. CELL GENOMICS 2022; 2:None. [PMID: 35983101 PMCID: PMC9365758 DOI: 10.1016/j.xgen.2022.100163] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Revised: 03/30/2022] [Accepted: 07/06/2022] [Indexed: 10/27/2022]
Abstract
Eukaryotic genomes vary in terms of size, chromosome number, and genetic complexity. Their temporal organization is complex, reflecting coordination between DNA folding and function. Here, we used fused karyotypes of budding yeast to characterize the effects of chromosome length on nuclear architecture. We found that size-matched megachromosomes expand to occupy a larger fraction of the enlarged nucleus. Hi-C maps reveal changes in the three-dimensional structure corresponding to inactivated centromeres and telomeres. De-clustering of inactive centromeres results in their loss of early replication, highlighting a functional correlation between genome organization and replication timing. Repositioning of former telomere-proximal regions on chromosome arms exposed a subset of contacts between flocculin genes. Chromatin reorganization of megachromosomes during cell division remained unperturbed, and it revealed that centromere-rDNA contacts in anaphase, extending over 0.3 Mb on wild-type chromosome, cannot exceed ∼1.7 Mb. Our results highlight the relevance of engineered karyotypes to unveiling relationships between genome organization and function.
Collapse
|
11
|
Claussin C, Vazquez J, Whitehouse I. Single-molecule mapping of replisome progression. Mol Cell 2022; 82:1372-1382.e4. [PMID: 35240057 PMCID: PMC8995386 DOI: 10.1016/j.molcel.2022.02.010] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Revised: 12/22/2021] [Accepted: 02/02/2022] [Indexed: 10/19/2022]
Abstract
Fundamental aspects of DNA replication, such as the anatomy of replication stall sites, how replisomes are influenced by gene transcription, and whether the progression of sister replisomes is coordinated, are poorly understood. Available techniques do not allow the precise mapping of the positions of individual replisomes on chromatin. We have developed a method called Replicon-seq that entails the excision of full-length replicons by controlled nuclease cleavage at replication forks. Replicons are sequenced using Nanopore, which provides a single-molecule readout of long DNA. Using Replicon-seq, we found that sister replisomes function autonomously and yet progress through chromatin with remarkable consistency. Replication forks that encounter obstacles pause for a short duration but rapidly resume synthesis. The helicase Rrm3 plays a critical role both in mitigating the effect of protein barriers and with facilitating efficient termination. Replicon-seq provides a high-resolution means of defining how individual replisomes move across the genome.
Collapse
Affiliation(s)
- Clémence Claussin
- Molecular Biology Program, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA
| | - Jacob Vazquez
- Molecular Biology Program, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA
| | - Iestyn Whitehouse
- Molecular Biology Program, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA.
| |
Collapse
|
12
|
Joshi I, Peng J, Alvino G, Kwan E, Feng W. Exceptional origin activation revealed by comparative analysis in two laboratory yeast strains. PLoS One 2022; 17:e0263569. [PMID: 35157703 PMCID: PMC8843211 DOI: 10.1371/journal.pone.0263569] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Accepted: 01/21/2022] [Indexed: 11/18/2022] Open
Abstract
We performed a comparative analysis of replication origin activation by genome-wide single-stranded DNA mapping in two yeast strains challenged by hydroxyurea, an inhibitor of the ribonucleotide reductase. We gained understanding of the impact on origin activation by three factors: S-phase checkpoint control, DNA sequence polymorphisms, and relative positioning of origin and transcription unit. Wild type W303 showed a significant reduction of fork progression accompanied by an elevated level of Rad53 phosphorylation as well as physical presence at origins compared to A364a. Moreover, a rad53K227A mutant in W303 activated more origins, accompanied by global reduction of ssDNA across all origins, compared to A364a. Sequence polymorphism in the consensus motifs of origins plays a minor role in determining strain-specific activity. Finally, we identified a new class of origins only active in checkpoint-proficient cells, which we named “Rad53-dependent origins”. Our study presents a comprehensive list of differentially used origins and provide new insights into the mechanisms of origin activation.
Collapse
Affiliation(s)
- Ishita Joshi
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, United States of America
| | - Jie Peng
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, United States of America
| | - Gina Alvino
- Department of Genome Sciences, University of Washington, Seattle, Washington, United States of America
| | - Elizabeth Kwan
- Department of Genome Sciences, University of Washington, Seattle, Washington, United States of America
| | - Wenyi Feng
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, United States of America
- * E-mail:
| |
Collapse
|
13
|
Ziane R, Camasses A, Radman-Livaja M. The asymmetric distribution of RNA polymerase II and nucleosomes on replicated daughter genomes is caused by differences in replication timing between the lagging and the leading strand. Genome Res 2022; 32:337-356. [PMID: 35042724 PMCID: PMC8805712 DOI: 10.1101/gr.275387.121] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2021] [Accepted: 12/19/2021] [Indexed: 11/24/2022]
Abstract
Chromatin features are thought to have a role in the epigenetic transmission of transcription states from one cell generation to the next. It is unclear how chromatin structure survives disruptions caused by genomic replication or whether chromatin features are instructive of the transcription state of the underlying gene. We developed a method to monitor budding yeast replication, transcription, and chromatin maturation dynamics on each daughter genome in parallel, with which we identified clusters of secondary origins surrounding known origins. We found a difference in the timing of lagging and leading strand replication on the order of minutes at most yeast genes. We propose a model in which the majority of old histones and RNA polymerase II (RNAPII) bind to the gene copy that replicated first, while newly synthesized nucleosomes are assembled on the copy that replicated second. RNAPII enrichment then shifts to the sister copy that replicated second. The order of replication is largely determined by genic orientation: If transcription and replication are codirectional, the leading strand replicates first; if they are counterdirectional, the lagging strand replicates first. A mutation in the Mcm2 subunit of the replicative helicase Mcm2-7 that impairs Mcm2 interactions with histone H3 slows down replication forks but does not qualitatively change the asymmetry in nucleosome distribution observed in the WT. We propose that active transcription states are inherited simultaneously and independently of their underlying chromatin states through the recycling of the transcription machinery and old histones, respectively. Transcription thus actively contributes to the reestablishment of the active chromatin state.
Collapse
Affiliation(s)
- Rahima Ziane
- Institut de Génétique Moléculaire de Montpellier, UMR 5535, CNRS, 34293 Montpellier Cedex 5, France.,Université de Montpellier, 34090 Montpellier, France
| | - Alain Camasses
- Institut de Génétique Moléculaire de Montpellier, UMR 5535, CNRS, 34293 Montpellier Cedex 5, France.,Université de Montpellier, 34090 Montpellier, France
| | - Marta Radman-Livaja
- Institut de Génétique Moléculaire de Montpellier, UMR 5535, CNRS, 34293 Montpellier Cedex 5, France.,Université de Montpellier, 34090 Montpellier, France
| |
Collapse
|
14
|
Tan X, Wu X, Han M, Wang L, Xu L, Li B, Yuan Y. Yeast autonomously replicating sequence (ARS): Identification, function, and modification. Eng Life Sci 2021. [DOI: 10.1002/elsc.202000085] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Affiliation(s)
- Xiao‐Yu Tan
- Frontiers Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology Tianjin University Tianjin P. R. China
- Synthetic Biology Research Platform, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin) Tianjin University Tianjin P. R. China
| | - Xiao‐Le Wu
- Frontiers Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology Tianjin University Tianjin P. R. China
- Synthetic Biology Research Platform, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin) Tianjin University Tianjin P. R. China
| | - Ming‐Zhe Han
- Frontiers Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology Tianjin University Tianjin P. R. China
- Synthetic Biology Research Platform, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin) Tianjin University Tianjin P. R. China
| | - Li Wang
- Frontiers Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology Tianjin University Tianjin P. R. China
- Synthetic Biology Research Platform, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin) Tianjin University Tianjin P. R. China
| | - Li Xu
- Frontiers Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology Tianjin University Tianjin P. R. China
- Synthetic Biology Research Platform, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin) Tianjin University Tianjin P. R. China
| | - Bing‐Zhi Li
- Frontiers Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology Tianjin University Tianjin P. R. China
- Synthetic Biology Research Platform, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin) Tianjin University Tianjin P. R. China
| | - Ying‐Jin Yuan
- Frontiers Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology Tianjin University Tianjin P. R. China
- Synthetic Biology Research Platform, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin) Tianjin University Tianjin P. R. China
| |
Collapse
|
15
|
Maria H, Kapoor S, Liu T, Rusche LN. Conservation of a DNA Replication Motif among Phylogenetically Distant Budding Yeast Species. Genome Biol Evol 2021; 13:6300524. [PMID: 34132803 PMCID: PMC8290112 DOI: 10.1093/gbe/evab137] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/10/2021] [Indexed: 01/23/2023] Open
Abstract
Eukaryotic DNA replication begins at genomic loci termed origins, which are bound by the origin recognition complex (ORC). Although ORC is conserved across species, the sequence composition of origins is more varied. In the budding yeast Saccharomyces cerevisiae, the ORC-binding motif consists of an A/T-rich 17 bp “extended ACS” sequence adjacent to a B1 element composed of two 3-bp motifs. Similar sequences occur at origins in closely related species, but it is not clear when this type of replication origin arose and whether it predated a whole-genome duplication that occurred around 100 Ma in the budding yeast lineage. To address these questions, we identified the ORC-binding sequences in the nonduplicated species Torulaspora delbrueckii. We used chromatin immunoprecipitation followed by sequencing and identified 190 ORC-binding sites distributed across the eight T. delbrueckii chromosomes. Using these sites, we identified an ORC-binding motif that is nearly identical to the known motif in S. cerevisiae. We also found that the T. delbrueckii ORC-binding sites function as origins in T. delbrueckii when cloned onto a plasmid and that the motif is required for plasmid replication. Finally, we compared an S. cerevisiae origin with two T. delbrueckii ORC-binding sites and found that they conferred similar stabilities to a plasmid. These results reveal that the ORC-binding motif arose prior to the whole-genome duplication and has been maintained for over 100 Myr.
Collapse
Affiliation(s)
- Haniam Maria
- Department of Biological Sciences, State University of New York at Buffalo, New York, USA
| | - Shivali Kapoor
- Department of Biological Sciences, State University of New York at Buffalo, New York, USA
| | - Tao Liu
- Department of Biostatistics and Bioinformatics, Roswell Park Comprehensive Cancer Center, Buffalo, New York, USA
| | - Laura N Rusche
- Department of Biological Sciences, State University of New York at Buffalo, New York, USA
| |
Collapse
|
16
|
Lee PH, Osley MA. Who gets a license: DNA synthesis in quiescent cells re-entering the cell cycle. Curr Genet 2021; 67:539-543. [PMID: 33682029 DOI: 10.1007/s00294-021-01170-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Revised: 02/24/2021] [Accepted: 02/26/2021] [Indexed: 12/23/2022]
Abstract
The precise regulation of the entry into S phase is critical for preventing genome instability. The first step in the initiation of eukaryotic DNA synthesis occurs in G1 phase cells and involves the loading of the conserved MCM helicase onto multiple origins of replication in a process known as origin licensing. In proliferating metazoan cells, an origin-licensing checkpoint delays initiation until high levels of MCM loading occur, with excess origins being licensed. One function of this checkpoint is to ensure that S phase can be completed in the face of replication stress by activation of dormant MCM bound origins. However, when both metazoan and yeast cells enter S phase from quiescence or G0 phase, a non-growing but reversible cell cycle state, origins are significantly under-licensed. In metazoan cells, under-licensing is the result of a compromised origin-licensing checkpoint. In budding yeast, our study has revealed that under-licensing can be attributed to the chromatin structure at a class of origins that is inhibitory to the binding of MCM. Thus, defects in multiple pathways may contribute to the failure to fully license origins in quiescent cells re-entering the cell cycle, thereby promoting a higher risk of genome instability.
Collapse
Affiliation(s)
- Po-Hsuen Lee
- Molecular Genetics and Microbiology, University of New Mexico Health Sciences Center, Albuquerque, NM, 87131, USA
| | - Mary Ann Osley
- Molecular Genetics and Microbiology, University of New Mexico Health Sciences Center, Albuquerque, NM, 87131, USA.
| |
Collapse
|
17
|
Lee PH, Osley M. Chromatin structure restricts origin utilization when quiescent cells re-enter the cell cycle. Nucleic Acids Res 2021; 49:864-878. [PMID: 33367871 PMCID: PMC7826286 DOI: 10.1093/nar/gkaa1148] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Revised: 11/04/2020] [Accepted: 12/21/2020] [Indexed: 12/12/2022] Open
Abstract
Quiescent cells reside in G0 phase, which is characterized by the absence of cell growth and proliferation. These cells remain viable and re-enter the cell cycle when prompted by appropriate signals. Using a budding yeast model of cellular quiescence, we investigated the program that initiated DNA replication when these G0 cells resumed growth. Quiescent cells contained very low levels of replication initiation factors, and their entry into S phase was delayed until these factors were re-synthesized. A longer S phase in these cells correlated with the activation of fewer origins of replication compared to G1 cells. The chromatin structure around inactive origins in G0 cells showed increased H3 occupancy and decreased nucleosome positioning compared to the same origins in G1 cells, inhibiting the origin binding of the Mcm4 subunit of the MCM licensing factor. Thus, quiescent yeast cells are under-licensed during their re-entry into S phase.
Collapse
Affiliation(s)
- Po-Hsuen Lee
- Department of Molecular Genetics and Microbiology University of New Mexico Health Sciences Center, Albuquerque, NM 87131, USA
| | - Mary Ann Osley
- Department of Molecular Genetics and Microbiology University of New Mexico Health Sciences Center, Albuquerque, NM 87131, USA
| |
Collapse
|
18
|
Cerritelli SM, Iranzo J, Sharma S, Chabes A, Crouch RJ, Tollervey D, El Hage A. High density of unrepaired genomic ribonucleotides leads to Topoisomerase 1-mediated severe growth defects in absence of ribonucleotide reductase. Nucleic Acids Res 2020; 48:4274-4297. [PMID: 32187369 PMCID: PMC7192613 DOI: 10.1093/nar/gkaa103] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2019] [Revised: 02/05/2020] [Accepted: 02/07/2020] [Indexed: 12/12/2022] Open
Abstract
Cellular levels of ribonucleoside triphosphates (rNTPs) are much higher than those of deoxyribonucleoside triphosphates (dNTPs), thereby influencing the frequency of incorporation of ribonucleoside monophosphates (rNMPs) by DNA polymerases (Pol) into DNA. RNase H2-initiated ribonucleotide excision repair (RER) efficiently removes single rNMPs in genomic DNA. However, processing of rNMPs by Topoisomerase 1 (Top1) in absence of RER induces mutations and genome instability. Here, we greatly increased the abundance of genomic rNMPs in Saccharomyces cerevisiae by depleting Rnr1, the major subunit of ribonucleotide reductase, which converts ribonucleotides to deoxyribonucleotides. We found that in strains that are depleted of Rnr1, RER-deficient, and harbor an rNTP-permissive replicative Pol mutant, excessive accumulation of single genomic rNMPs severely compromised growth, but this was reversed in absence of Top1. Thus, under Rnr1 depletion, limited dNTP pools slow DNA synthesis by replicative Pols and provoke the incorporation of high levels of rNMPs in genomic DNA. If a threshold of single genomic rNMPs is exceeded in absence of RER and presence of limited dNTP pools, Top1-mediated genome instability leads to severe growth defects. Finally, we provide evidence showing that accumulation of RNA/DNA hybrids in absence of RNase H1 and RNase H2 leads to cell lethality under Rnr1 depletion.
Collapse
Affiliation(s)
- Susana M Cerritelli
- SFR, Division of Intramural Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
| | - Jaime Iranzo
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, USA
| | - Sushma Sharma
- Department of Medical Biochemistry and Biophysics, Umeå University, Umeå SE-901 87, Sweden
| | - Andrei Chabes
- Department of Medical Biochemistry and Biophysics, Umeå University, Umeå SE-901 87, Sweden
| | - Robert J Crouch
- SFR, Division of Intramural Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
| | - David Tollervey
- The Wellcome Centre for Cell Biology, University of Edinburgh, Edinburgh, UK
| | - Aziz El Hage
- The Wellcome Centre for Cell Biology, University of Edinburgh, Edinburgh, UK
| |
Collapse
|
19
|
Do DT, Le NQK. Using extreme gradient boosting to identify origin of replication in Saccharomyces cerevisiae via hybrid features. Genomics 2020; 112:2445-2451. [PMID: 31987913 DOI: 10.1016/j.ygeno.2020.01.017] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2019] [Revised: 01/12/2020] [Accepted: 01/23/2020] [Indexed: 12/11/2022]
Abstract
DNA replication is a fundamental task that plays a crucial role in the propagation of all living things on earth. Hence, the accurate identification of its origin could be the key to giving an insightful understanding of the regulatory mechanism of gene expression. Indeed, with the robust development of computational techniques and the abundant biological sequencing data, it has become possible for scientists to identify the origin of replication accurately and promptly. This growing concern has drawn a lot of attention among experts in this field. However, to gain better outcomes, more work is required. Therefore, this study is designed to explore the combination of state-of-the-art features and extreme gradient boosting learning system in classifying DNA sequences. Our hybrid approach is able to identify the origin of DNA replication with achieved sensitivity of 85.19%, specificity of 93.83%, accuracy of 89.51%, and MCC of 0.7931. Evidence is presented to show that our proposed method is superior to the state-of-the-art methods on the same benchmark dataset. Moreover, the research results represent a further step towards developing the prediction models for DNA replication in particular and DNA sequences in general.
Collapse
Affiliation(s)
- Duyen Thi Do
- Toxicology and Biomedicine Research Group, Faculty of Applied Sciences, Ton Duc Thang University, Ho Chi Minh City, Viet Nam.
| | - Nguyen Quoc Khanh Le
- Professional Master Program in Artificial Intelligence in Medicine, College of Medicine, Taipei Medical University, Taipei City 106, Taiwan; Research Center of Artificial Intelligence in Medicine, Taipei Medical University, Taipei City 106, Taiwan.
| |
Collapse
|
20
|
Ng CT, Gan L. Investigating eukaryotic cells with cryo-ET. Mol Biol Cell 2020; 31:87-100. [PMID: 31935172 PMCID: PMC6960407 DOI: 10.1091/mbc.e18-05-0329] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2019] [Revised: 11/25/2019] [Accepted: 11/29/2019] [Indexed: 01/06/2023] Open
Abstract
The interior of eukaryotic cells is mysterious. How do the large communities of macromolecular machines interact with each other? How do the structures and positions of these nanoscopic entities respond to new stimuli? Questions like these can now be answered with the help of a method called electron cryotomography (cryo-ET). Cryo-ET will ultimately reveal the inner workings of a cell at the protein, secondary structure, and perhaps even side-chain levels. Combined with genetic or pharmacological perturbation, cryo-ET will allow us to answer previously unimaginable questions, such as how structure, biochemistry, and forces are related in situ. Because it bridges structural biology and cell biology, cryo-ET is indispensable for structural cell biology-the study of the 3-D macromolecular structure of cells. Here we discuss some of the key ideas, strategies, auxiliary techniques, and innovations that an aspiring structural cell biologist will consider when planning to ask bold questions.
Collapse
Affiliation(s)
- Cai Tong Ng
- Department of Biological Sciences and Centre for BioImaging Sciences, National University of Singapore, Singapore 117543
| | - Lu Gan
- Department of Biological Sciences and Centre for BioImaging Sciences, National University of Singapore, Singapore 117543
| |
Collapse
|
21
|
Yousefi R, Rowicka M. Stochasticity of replication forks' speeds plays a key role in the dynamics of DNA replication. PLoS Comput Biol 2019; 15:e1007519. [PMID: 31869320 PMCID: PMC6975548 DOI: 10.1371/journal.pcbi.1007519] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Revised: 01/22/2020] [Accepted: 10/29/2019] [Indexed: 11/26/2022] Open
Abstract
Eukaryotic DNA replication is elaborately orchestrated to duplicate the genome timely and faithfully. Replication initiates at multiple origins from which replication forks emanate and travel bi-directionally. The complex spatio-temporal regulation of DNA replication remains incompletely understood. To study it, computational models of DNA replication have been developed in S. cerevisiae. However, in spite of the experimental evidence of forks’ speed stochasticity, all models assumed that forks’ speeds are the same. Here, we present the first model of DNA replication assuming that speeds vary stochastically between forks. Utilizing data from both wild-type and hydroxyurea-treated yeast cells, we show that our model is more accurate than models assuming constant forks’ speed and reconstructs dynamics of DNA replication faithfully starting both from population-wide data and data reflecting fork movement in individual cells. Completion of replication in a timely manner is a challenge due to its stochasticity; we propose an empirically derived modification to replication speed based on the distance to the approaching fork, which promotes timely completion of replication. In summary, our work discovers a key role that stochasticity of the forks’ speed plays in the dynamics of DNA replication. We show that without including stochasticity of forks’ speed it is not possible to accurately reconstruct movement of individual replication forks, measured by DNA combing. DNA replication in eukaryotes starts from multiple sites termed replication origins. Replication timing at individual sites is stochastic, but reproducible population-wide. Complex and not yet completely understood mechanisms ensure that genome is replicated exactly once and that replication is finished in time. This complex spatio-temporal organization of DNA replication makes computational modeling a useful tool to study replication mechanisms. For simplicity, all previous models assumed constant replication forks’ speed. Here, we show that such models are incapable of accurately reconstructing distances travelled by individual replication forks. Therefore, we propose a model assuming that replication speed varies stochastically between forks. We show that such model reproduces faithfully distances travelled by individual replication forks. Moreover, our model is simpler than previous model and thus avoids over-learning (fitting noise). We also discover how replication speed may be attuned to timely complete replication. We propose that forks’ speed increases with diminishing distance to the approaching fork, which we show promotes timely completion of replication. Such speed up can be e.g. explained by a synergy effect of chromatin unwinding by both forks. Our model can be used to simulate phenomena beyond replication, e.g. DNA double-strand breaks resulting from broken replication forks.
Collapse
Affiliation(s)
- Razie Yousefi
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch at Galveston, Galveston, Texas, United States of America
| | - Maga Rowicka
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch at Galveston, Galveston, Texas, United States of America
- Institute of Translational Sciences, University of Texas Medical Branch at Galveston, Galveston, Texas, United States of America
- * E-mail:
| |
Collapse
|
22
|
Wang D, Gao F. Comprehensive Analysis of Replication Origins in Saccharomyces cerevisiae Genomes. Front Microbiol 2019; 10:2122. [PMID: 31572328 PMCID: PMC6753640 DOI: 10.3389/fmicb.2019.02122] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2018] [Accepted: 08/29/2019] [Indexed: 12/15/2022] Open
Abstract
DNA replication initiates from multiple replication origins (ORIs) in eukaryotes. Discovery and characterization of replication origins are essential for a better understanding of the molecular mechanism of DNA replication. In this study, the features of autonomously replicating sequences (ARSs) in Saccharomyces cerevisiae have been comprehensively analyzed as follows. Firstly, we carried out the analysis of the ARSs available in S. cerevisiae S288C. By evaluating the sequence similarity of experimentally established ARSs, we found that 94.32% of ARSs are unique across the whole genome of S. cerevisiae S288C and those with high sequence similarity are prone to locate in subtelomeres. Subsequently, we built a non-redundant dataset with a total of 520 ARSs, which are based on ARSs annotation of S. cerevisiae S288C from SGD and then supplemented with those from OriDB and DeOri databases. We conducted a large-scale comparison of ORIs among the diverse budding yeast strains from a population genomics perspective. We found that 82.7% of ARSs are not only conserved in genomic sequence but also relatively conserved in chromosomal position. The non-conserved ARSs tend to distribute in the subtelomeric regions. We also conducted a pan-genome analysis of ARSs among the S. cerevisiae strains, and a total of 183 core ARSs existing in all yeast strains were determined. We extracted the genes adjacent to replication origins among the 104 yeast strains to examine whether there are differences in their gene functions. The result showed that the genes involved in the initiation of DNA replication, such as orc3, mcm2, mcm4, mcm6, and cdc45, are conservatively located adjacent to the replication origins. Furthermore, we found the genes adjacent to conserved ARSs are significantly enriched in DNA binding, enzyme activity, transportation, and energy, whereas for the genes adjacent to non-conserved ARSs are significantly enriched in response to environmental stress, metabolites biosynthetic process and biosynthesis of antibiotics. In general, we characterized the replication origins from the genome-wide and population genomics perspectives, which would provide new insights into the replication mechanism of S. cerevisiae and facilitate the design of algorithms to identify genome-wide replication origins in yeast.
Collapse
Affiliation(s)
- Dan Wang
- Department of Physics, School of Science, Tianjin University, Tianjin, China
| | - Feng Gao
- Department of Physics, School of Science, Tianjin University, Tianjin, China.,Key Laboratory of Systems Bioengineering, Ministry of Education, Tianjin University, Tianjin, China.,SynBio Research Platform, Collaborative Innovation Center of Chemical Science and Engineering, Tianjin, China
| |
Collapse
|
23
|
Dao FY, Lv H, Wang F, Ding H. Recent Advances on the Machine Learning Methods in Identifying DNA Replication Origins in Eukaryotic Genomics. Front Genet 2018; 9:613. [PMID: 30619452 PMCID: PMC6295579 DOI: 10.3389/fgene.2018.00613] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2018] [Accepted: 11/21/2018] [Indexed: 01/01/2023] Open
Abstract
The initiate site of DNA replication is called origins of replication (ORI) which is regulated by a set of regulatory proteins and plays important roles in the basic biochemical process during cell growth and division in all living organisms. Therefore, the study of ORIs is essential for understanding the cell-division cycle and gene expression regulation so that scholars can develop a new strategy against genetic diseases by using the knowledge of DNA replication. Thus, the accurate identification of ORIs will provide key clues for DNA replication research and clinical medicine. Although, the conventional experiments could provide accurate results, they are time-consuming and cost ineffective. On the contrary, bioinformatics-based methods can overcome these shortcomings. Especially, with the emergence of DNA sequences in the post-genomic era, it is highly expected to develop high throughput tools to identify ORIs based on sequence information. In this review, we will summarize the current progress in computational prediction of eukaryotic ORIs including the collection of benchmark dataset, the application of machine learning-based techniques, the results obtained by these methods, and the construction of web servers. Finally, we gave the future perspectives on ORIs prediction. The review provided readers with a whole background of ORIs prediction based on machine learning methods, which will be helpful for researchers to study DNA replication in-depth and drug therapy of genetic defect.
Collapse
Affiliation(s)
- Fu-Ying Dao
- Key Laboratory for Neuro-Information of Ministry of Education, School of Life Science and Technology, Center for Informational Biology, University of Electronic Science and Technology of China, Chengdu, China
| | - Hao Lv
- Key Laboratory for Neuro-Information of Ministry of Education, School of Life Science and Technology, Center for Informational Biology, University of Electronic Science and Technology of China, Chengdu, China
| | - Fang Wang
- Key Laboratory for Neuro-Information of Ministry of Education, School of Life Science and Technology, Center for Informational Biology, University of Electronic Science and Technology of China, Chengdu, China
| | - Hui Ding
- Key Laboratory for Neuro-Information of Ministry of Education, School of Life Science and Technology, Center for Informational Biology, University of Electronic Science and Technology of China, Chengdu, China
| |
Collapse
|
24
|
Dao FY, Lv H, Wang F, Feng CQ, Ding H, Chen W, Lin H. Identify origin of replication in Saccharomyces cerevisiae using two-step feature selection technique. Bioinformatics 2018; 35:2075-2083. [DOI: 10.1093/bioinformatics/bty943] [Citation(s) in RCA: 147] [Impact Index Per Article: 24.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2018] [Revised: 11/06/2018] [Accepted: 11/13/2018] [Indexed: 02/07/2023] Open
Affiliation(s)
- Fu-Ying Dao
- Key Laboratory for NeuroInformation of Ministry of Education, School of Life Science and Technology and Center for Informational Biology, University of Electronic Science and Technology of China, Chengdu, China
| | - Hao Lv
- Key Laboratory for NeuroInformation of Ministry of Education, School of Life Science and Technology and Center for Informational Biology, University of Electronic Science and Technology of China, Chengdu, China
| | - Fang Wang
- Key Laboratory for NeuroInformation of Ministry of Education, School of Life Science and Technology and Center for Informational Biology, University of Electronic Science and Technology of China, Chengdu, China
| | - Chao-Qin Feng
- Key Laboratory for NeuroInformation of Ministry of Education, School of Life Science and Technology and Center for Informational Biology, University of Electronic Science and Technology of China, Chengdu, China
| | - Hui Ding
- Key Laboratory for NeuroInformation of Ministry of Education, School of Life Science and Technology and Center for Informational Biology, University of Electronic Science and Technology of China, Chengdu, China
| | - Wei Chen
- Key Laboratory for NeuroInformation of Ministry of Education, School of Life Science and Technology and Center for Informational Biology, University of Electronic Science and Technology of China, Chengdu, China
- Innovative Institute of Chinese Medicine and Pharmacy, Chengdu University of Traditional Chinese Medicine, Chengdu, China
| | - Hao Lin
- Key Laboratory for NeuroInformation of Ministry of Education, School of Life Science and Technology and Center for Informational Biology, University of Electronic Science and Technology of China, Chengdu, China
| |
Collapse
|
25
|
Hiraga SI, Monerawela C, Katou Y, Shaw S, Clark KR, Shirahige K, Donaldson AD. Budding yeast Rif1 binds to replication origins and protects DNA at blocked replication forks. EMBO Rep 2018; 19:e46222. [PMID: 30104203 PMCID: PMC6123642 DOI: 10.15252/embr.201846222] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2018] [Revised: 07/17/2018] [Accepted: 07/23/2018] [Indexed: 11/28/2022] Open
Abstract
Despite its evolutionarily conserved function in controlling DNA replication, the chromosomal binding sites of the budding yeast Rif1 protein are not well understood. Here, we analyse genome-wide binding of budding yeast Rif1 by chromatin immunoprecipitation, during G1 phase and in S phase with replication progressing normally or blocked by hydroxyurea. Rif1 associates strongly with telomeres through interaction with Rap1. By comparing genomic binding of wild-type Rif1 and truncated Rif1 lacking the Rap1-interaction domain, we identify hundreds of Rap1-dependent and Rap1-independent chromosome interaction sites. Rif1 binds to centromeres, highly transcribed genes and replication origins in a Rap1-independent manner, associating with both early and late-initiating origins. Interestingly, Rif1 also binds around activated origins when replication progression is blocked by hydroxyurea, suggesting association with blocked forks. Using nascent DNA labelling and DNA combing techniques, we find that in cells treated with hydroxyurea, yeast Rif1 stabilises recently synthesised DNA Our results indicate that, in addition to controlling DNA replication initiation, budding yeast Rif1 plays an ongoing role after initiation and controls events at blocked replication forks.
Collapse
Affiliation(s)
| | | | - Yuki Katou
- Institute for Quantitative Biosciences, University of Tokyo, Tokyo, Japan
| | - Sophie Shaw
- Centre for Genome-Enabled Biology and Medicine, University of Aberdeen, Aberdeen, UK
| | - Kate Rm Clark
- Institute of Medical Sciences, University of Aberdeen, Aberdeen, UK
| | | | - Anne D Donaldson
- Institute of Medical Sciences, University of Aberdeen, Aberdeen, UK
| |
Collapse
|
26
|
Voichek Y, Mittelman K, Gordon Y, Bar-Ziv R, Lifshitz Smit D, Shenhav R, Barkai N. Epigenetic Control of Expression Homeostasis during Replication Is Stabilized by the Replication Checkpoint. Mol Cell 2018; 70:1121-1133.e9. [PMID: 29910110 DOI: 10.1016/j.molcel.2018.05.015] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2017] [Revised: 03/22/2018] [Accepted: 05/11/2018] [Indexed: 11/24/2022]
Abstract
DNA replication introduces a dosage imbalance between early and late replicating genes. In budding yeast, buffering gene expression against this imbalance depends on marking replicated DNA by H3K56 acetylation (H3K56ac). Whether additional processes are required for suppressing transcription from H3K56ac-labeled DNA remains unknown. Here, using a database-guided candidate screen, we find that COMPASS, the H3K4 methyltransferase, and its upstream effector, PAF1C, act downstream of H3K56ac to buffer expression. Replicated genes show reduced abundance of the transcription activating mark H3K4me3 and accumulate the transcription inhibitory mark H3K4me2 near transcription start sites. Notably, in hydroxyurea-exposed cells, the S phase checkpoint stabilizes H3K56ac and becomes essential for buffering. We suggest that H3K56ac suppresses transcription of replicated genes by interfering with post-replication recovery of epigenetic marks and assign a new function for the S phase checkpoint in stabilizing this mechanism during persistent dosage imbalance.
Collapse
Affiliation(s)
- Yoav Voichek
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Karin Mittelman
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Yulia Gordon
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Raz Bar-Ziv
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - David Lifshitz Smit
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Rom Shenhav
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Naama Barkai
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel.
| |
Collapse
|
27
|
iOri-Human: identify human origin of replication by incorporating dinucleotide physicochemical properties into pseudo nucleotide composition. Oncotarget 2018; 7:69783-69793. [PMID: 27626500 PMCID: PMC5342515 DOI: 10.18632/oncotarget.11975] [Citation(s) in RCA: 157] [Impact Index Per Article: 26.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Accepted: 09/06/2016] [Indexed: 02/07/2023] Open
Abstract
The initiation of replication is an extremely important process in DNA life cycle. Given an uncharacterized DNA sequence, can we identify where its origin of replication (ORI) is located? It is no doubt a fundamental problem in genome analysis. Particularly, with the rapid development of genome sequencing technology that results in a huge amount of sequence data, it is highly desired to develop computational methods for rapidly and effectively identifying the ORIs in these genomes. Unfortunately, by means of the existing computational methods, such as sequence alignment or kmer strategies, it could hardly achieve decent success rates. To address this problem, we developed a predictor called “iOri-Human”. Rigorous jackknife tests have shown that its overall accuracy and stability in identifying human ORIs are over 75% and 50%, respectively. In the predictor, it is through the pseudo nucleotide composition (an extension of pseudo amino acid composition) that 96 physicochemical properties for the 16 possible constituent dinucleotides have been incorporated to reflect the global sequence patterns in DNA as well as its local sequence patterns. Moreover, a user-friendly web-server for iOri-Human has been established at http://lin.uestc.edu.cn/server/iOri-Human.html, by which users can easily get their desired results without the need to through the complicated mathematics involved.
Collapse
|
28
|
Rodriguez J, Lee L, Lynch B, Tsukiyama T. Nucleosome occupancy as a novel chromatin parameter for replication origin functions. Genome Res 2016; 27:269-277. [PMID: 27895110 PMCID: PMC5287232 DOI: 10.1101/gr.209940.116] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2016] [Accepted: 11/17/2016] [Indexed: 11/01/2022]
Abstract
Eukaryotic DNA replication initiates from multiple discrete sites in the genome, termed origins of replication (origins). Prior to S phase, multiple origins are poised to initiate replication by recruitment of the pre-replicative complex (pre-RC). For proper replication to occur, origin activation must be tightly regulated. At the population level, each origin has a distinct firing time and frequency of activation within S phase. Many studies have shown that chromatin can strongly influence initiation of DNA replication. However, the chromatin parameters that affect properties of origins have not been thoroughly established. We found that nucleosome occupancy in G1 varies greatly around origins across the S. cerevisiae genome, and nucleosome occupancy around origins significantly correlates with the activation time and efficiency of origins, as well as pre-RC formation. We further demonstrate that nucleosome occupancy around origins in G1 is established during transition from G2/M to G1 in a pre-RC-dependent manner. Importantly, the diminished cell-cycle changes in nucleosome occupancy around origins in the orc1-161 mutant are associated with an abnormal global origin usage profile, suggesting that proper establishment of nucleosome occupancy around origins is a critical step for regulation of global origin activities. Our work thus establishes nucleosome occupancy as a novel and key chromatin parameter for proper origin regulation.
Collapse
Affiliation(s)
- Jairo Rodriguez
- Basic Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109, USA
| | - Laura Lee
- Basic Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109, USA.,Molecular and Cellular Biology Program, University of Washington, Seattle, Washington 98195, USA
| | - Bryony Lynch
- Basic Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109, USA
| | - Toshio Tsukiyama
- Basic Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109, USA
| |
Collapse
|
29
|
Vasseur P, Tonazzini S, Ziane R, Camasses A, Rando OJ, Radman-Livaja M. Dynamics of Nucleosome Positioning Maturation following Genomic Replication. Cell Rep 2016; 16:2651-2665. [PMID: 27568571 PMCID: PMC5014762 DOI: 10.1016/j.celrep.2016.07.083] [Citation(s) in RCA: 64] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Revised: 03/22/2016] [Accepted: 07/28/2016] [Indexed: 12/31/2022] Open
Abstract
Chromatin is thought to carry epigenetic information from one generation to the next, although it is unclear how such information survives the disruptions of nucleosomal architecture occurring during genomic replication. Here, we measure a key aspect of chromatin structure dynamics during replication—how rapidly nucleosome positions are established on the newly replicated daughter genomes. By isolating newly synthesized DNA marked with 5-ethynyl-2′-deoxyuridine (EdU), we characterize nucleosome positions on both daughter genomes of S. cerevisiae during chromatin maturation. We find that nucleosomes rapidly adopt their mid-log positions at highly transcribed genes, which is consistent with a role for transcription in positioning nucleosomes in vivo. Additionally, experiments in hir1Δ mutants reveal a role for HIR in nucleosome spacing. We also characterized nucleosome positions on the leading and lagging strands, uncovering differences in chromatin maturation dynamics at hundreds of genes. Our data define the maturation dynamics of newly replicated chromatin and support a role for transcription in sculpting the chromatin template. Nucleosome positions are determined on newly replicated DNA Transcription reorders nucleosomes in gene bodies after DNA replication The HIR complex tightens nucleosome spacing in gene bodies following replication Nucleosome positions on leading and lagging strands depend on genes’ orientation
Collapse
Affiliation(s)
- Pauline Vasseur
- Institut de Génétique Moléculaire de Montpellier, UMR 5535 CNRS, 1919 Route de Mende, 34293 Montpellier Cedex 5, France; Université de Montpellier, 163 rue Auguste Broussonnet, 34090 Montpellier, France
| | - Saphia Tonazzini
- Institut de Génétique Moléculaire de Montpellier, UMR 5535 CNRS, 1919 Route de Mende, 34293 Montpellier Cedex 5, France; Université de Montpellier, 163 rue Auguste Broussonnet, 34090 Montpellier, France
| | - Rahima Ziane
- Institut de Génétique Moléculaire de Montpellier, UMR 5535 CNRS, 1919 Route de Mende, 34293 Montpellier Cedex 5, France; Université de Montpellier, 163 rue Auguste Broussonnet, 34090 Montpellier, France
| | - Alain Camasses
- Institut de Génétique Moléculaire de Montpellier, UMR 5535 CNRS, 1919 Route de Mende, 34293 Montpellier Cedex 5, France; Université de Montpellier, 163 rue Auguste Broussonnet, 34090 Montpellier, France
| | - Oliver J Rando
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Marta Radman-Livaja
- Institut de Génétique Moléculaire de Montpellier, UMR 5535 CNRS, 1919 Route de Mende, 34293 Montpellier Cedex 5, France; Université de Montpellier, 163 rue Auguste Broussonnet, 34090 Montpellier, France.
| |
Collapse
|
30
|
Abstract
DNA replication origins strikingly differ between eukaryotic species and cell types. Origins are localized and can be highly efficient in budding yeast, are randomly located in early fly and frog embryos, which do not transcribe their genomes, and are clustered in broad (10-100 kb) non-transcribed zones, frequently abutting transcribed genes, in mammalian cells. Nonetheless, in all cases, origins are established during the G1-phase of the cell cycle by the loading of double hexamers of the Mcm 2-7 proteins (MCM DHs), the core of the replicative helicase. MCM DH activation in S-phase leads to origin unwinding, polymerase recruitment, and initiation of bidirectional DNA synthesis. Although MCM DHs are initially loaded at sites defined by the binding of the origin recognition complex (ORC), they ultimately bind chromatin in much greater numbers than ORC and only a fraction are activated in any one S-phase. Data suggest that the multiplicity and functional redundancy of MCM DHs provide robustness to the replication process and affect replication time and that MCM DHs can slide along the DNA and spread over large distances around the ORC. Recent studies further show that MCM DHs are displaced along the DNA by collision with transcription complexes but remain functional for initiation after displacement. Therefore, eukaryotic DNA replication relies on intrinsically mobile and flexible origins, a strategy fundamentally different from bacteria but conserved from yeast to human. These properties of MCM DHs likely contribute to the establishment of broad, intergenic replication initiation zones in higher eukaryotes.
Collapse
Affiliation(s)
- Olivier Hyrien
- Institut de Biologie de l'Ecole Normale Superieure (IBENS), Ecole Normale Superieure, PSL Research University, Paris, France
| |
Collapse
|
31
|
Bar-Ziv R, Voichek Y, Barkai N. Chromatin dynamics during DNA replication. Genome Res 2016; 26:1245-56. [PMID: 27225843 PMCID: PMC5052047 DOI: 10.1101/gr.201244.115] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2015] [Accepted: 05/23/2016] [Indexed: 01/21/2023]
Abstract
Chromatin is composed of DNA and histones, which provide a unified platform for regulating DNA-related processes, mostly through their post-translational modification. During DNA replication, histone arrangement is perturbed, first to allow progression of DNA polymerase and then during repackaging of the replicated DNA. To study how DNA replication influences the pattern of histone modification, we followed the cell-cycle dynamics of 10 histone marks in budding yeast. We find that histones deposited on newly replicated DNA are modified at different rates: While some marks appear immediately upon replication (e.g., H4K16ac, H3K4me1), others increase with transcription-dependent delays (e.g., H3K4me3, H3K36me3). Notably, H3K9ac was deposited as a wave preceding the replication fork by ∼5–6 kb. This replication-guided H3K9ac was fully dependent on the acetyltransferase Rtt109, while expression-guided H3K9ac was deposited by Gcn5. Further, topoisomerase depletion intensified H3K9ac in front of the replication fork and in sites where RNA polymerase II was trapped, suggesting supercoiling stresses trigger H3K9 acetylation. Our results assign complementary roles for DNA replication and gene expression in defining the pattern of histone modification.
Collapse
Affiliation(s)
- Raz Bar-Ziv
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Yoav Voichek
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Naama Barkai
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| |
Collapse
|
32
|
Abstract
Young et al., (2010) showed that due to gene length bias the popular Fisher Exact Test should not be used to study the association between a group of differentially expressed (DE) genes and a specific Gene Ontology (GO) category. Instead they suggest a test where one conditions on the genes in the GO category and draws the pseudo DE expressed genes according to a length-dependent distribution. The same model was presented in a different context by Kazemian et al., (2011) who went on to offer a dynamic programming (DP) algorithm to exactly compute the significance of the proposed test. Here we point out that while valid, the test proposed by these authors is no longer symmetric as Fisher's Exact Test is: one gets different answers if one conditions on the observed GO category than on the DE set. As an alternative we offer a symmetric generalization of Fisher's Exact Test and provide efficient algorithms to evaluate its significance.
Collapse
Affiliation(s)
- David Manescu
- School of Mathematics and Statistics, University of Sydney , Sydney, Australia
| | - Uri Keich
- School of Mathematics and Statistics, University of Sydney , Sydney, Australia
| |
Collapse
|
33
|
Thierry A, Khanna V, Dujon B. Massive Amplification at an Unselected Locus Accompanies Complex Chromosomal Rearrangements in Yeast. G3 (BETHESDA, MD.) 2016; 6:1201-15. [PMID: 26945028 PMCID: PMC4856073 DOI: 10.1534/g3.115.024547] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/06/2015] [Accepted: 02/20/2016] [Indexed: 12/13/2022]
Abstract
Gene amplification has been observed in different organisms in response to environmental constraints, such as limited nutrients or exposure to a variety of toxic compounds, conferring them with specific phenotypic adaptations via increased expression levels. However, the presence of multiple gene copies in natural genomes has generally not been found in the absence of specific functional selection. Here, we show that the massive amplification of a chromosomal locus (up to 880 copies per cell) occurs in the absence of any direct selection, and is associated with low-order amplifications of flanking segments in complex chromosomal alterations. These results were obtained from mutants with restored phenotypes that spontaneously appeared from genetically engineered strains of the yeast Saccharomyces cerevisiae suffering from severe fitness reduction. Grossly extended chromosomes (macrotene) were formed, with complex structural alterations but sufficient stability to propagate unchanged over successive generations. Their detailed molecular analysis, including complete genome sequencing, identification of sequence breakpoints, and comparisons between mutants, revealed novel mechanisms causing their formation, whose combined action underlies the astonishing dynamics of eukaryotic chromosomes and their consequences.
Collapse
Affiliation(s)
- Agnès Thierry
- Institut Pasteur, Unité de Génétique Moléculaire des Levures, CNRS (UMR3525), Sorbonne Universités, UPMC, Université Paris 06 (UFR927), F-75724 CEDEX 15, France
| | - Varun Khanna
- Institut Pasteur, Unité de Génétique Moléculaire des Levures, CNRS (UMR3525), Sorbonne Universités, UPMC, Université Paris 06 (UFR927), F-75724 CEDEX 15, France
| | - Bernard Dujon
- Institut Pasteur, Unité de Génétique Moléculaire des Levures, CNRS (UMR3525), Sorbonne Universités, UPMC, Université Paris 06 (UFR927), F-75724 CEDEX 15, France
| |
Collapse
|
34
|
Chen W, Feng P, Ding H, Lin H, Chou KC. Using deformation energy to analyze nucleosome positioning in genomes. Genomics 2016; 107:69-75. [DOI: 10.1016/j.ygeno.2015.12.005] [Citation(s) in RCA: 87] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2015] [Revised: 12/06/2015] [Accepted: 12/22/2015] [Indexed: 12/28/2022]
|
35
|
Kubota T, Katou Y, Nakato R, Shirahige K, Donaldson AD. Replication-Coupled PCNA Unloading by the Elg1 Complex Occurs Genome-wide and Requires Okazaki Fragment Ligation. Cell Rep 2015. [PMID: 26212319 PMCID: PMC4534484 DOI: 10.1016/j.celrep.2015.06.066] [Citation(s) in RCA: 75] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
The sliding clamp PCNA is a crucial component of the DNA replication machinery. Timely PCNA loading and unloading are central for genome integrity and must be strictly coordinated with other DNA processing steps during replication. Here, we show that the S. cerevisiae Elg1 replication factor C-like complex (Elg1-RLC) unloads PCNA genome-wide following Okazaki fragment ligation. In the absence of Elg1, PCNA is retained on chromosomes in the wake of replication forks, rather than at specific sites. Degradation of the Okazaki fragment ligase Cdc9 leads to PCNA accumulation on chromatin, similar to the accumulation caused by lack of Elg1. We demonstrate that Okazaki fragment ligation is the critical prerequisite for PCNA unloading, since Chlorella virus DNA ligase can substitute for Cdc9 in yeast and simultaneously promotes PCNA unloading. Our results suggest that Elg1-RLC acts as a general PCNA unloader and is dependent upon DNA ligation during chromosome replication.
Collapse
Affiliation(s)
- Takashi Kubota
- Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, Scotland, UK.
| | - Yuki Katou
- Research Center for Epigenetic Disease, Institute of Molecular and Cellular Biosciences, The University of Tokyo, Tokyo 113-0032, Japan
| | - Ryuichiro Nakato
- Research Center for Epigenetic Disease, Institute of Molecular and Cellular Biosciences, The University of Tokyo, Tokyo 113-0032, Japan
| | - Katsuhiko Shirahige
- Research Center for Epigenetic Disease, Institute of Molecular and Cellular Biosciences, The University of Tokyo, Tokyo 113-0032, Japan
| | - Anne D Donaldson
- Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, Scotland, UK
| |
Collapse
|
36
|
Johnson RE, Klassen R, Prakash L, Prakash S. A Major Role of DNA Polymerase δ in Replication of Both the Leading and Lagging DNA Strands. Mol Cell 2015; 59:163-175. [PMID: 26145172 DOI: 10.1016/j.molcel.2015.05.038] [Citation(s) in RCA: 146] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2014] [Revised: 03/20/2015] [Accepted: 05/28/2015] [Indexed: 01/08/2023]
Abstract
Genetic studies with S. cerevisiae Polδ (pol3-L612M) and Polε (pol2-M644G) mutant alleles, each of which display a higher rate for the generation of a specific mismatch, have led to the conclusion that Polε is the primary leading strand replicase and that Polδ is restricted to replicating the lagging strand template. Contrary to this widely accepted view, here we show that Polδ plays a major role in the replication of both DNA strands, and that the paucity of pol3-L612M-generated errors on the leading strand results from their more proficient removal. Thus, the apparent lack of Polδ contribution to leading strand replication is due to differential mismatch removal rather than differential mismatch generation. Altogether, our genetic studies with Pol3 and Pol2 mutator alleles support the conclusion that Polδ, and not Polε, is the major DNA polymerase for carrying out both leading and lagging DNA synthesis.
Collapse
Affiliation(s)
- Robert E Johnson
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX 77555-1061, USA
| | - Roland Klassen
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX 77555-1061, USA
| | - Louise Prakash
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX 77555-1061, USA
| | - Satya Prakash
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX 77555-1061, USA
| |
Collapse
|
37
|
Mcm2-7 Is an Active Player in the DNA Replication Checkpoint Signaling Cascade via Proposed Modulation of Its DNA Gate. Mol Cell Biol 2015; 35:2131-43. [PMID: 25870112 DOI: 10.1128/mcb.01357-14] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2014] [Accepted: 04/05/2015] [Indexed: 01/01/2023] Open
Abstract
The DNA replication checkpoint (DRC) monitors and responds to stalled replication forks to prevent genomic instability. How core replication factors integrate into this phosphorylation cascade is incompletely understood. Here, through analysis of a unique mcm allele targeting a specific ATPase active site (mcm2DENQ), we show that the Mcm2-7 replicative helicase has a novel DRC function as part of the signal transduction cascade. This allele exhibits normal downstream mediator (Mrc1) phosphorylation, implying DRC sensor kinase activation. However, the mutant also exhibits defective effector kinase (Rad53) activation and classic DRC phenotypes. Our previous in vitro analysis showed that the mcm2DENQ mutation prevents a specific conformational change in the Mcm2-7 hexamer. We infer that this conformational change is required for its DRC role and propose that it allosterically facilitates Rad53 activation to ensure a replication-specific checkpoint response.
Collapse
|
38
|
Belsky JA, MacAlpine HK, Lubelsky Y, Hartemink AJ, MacAlpine DM. Genome-wide chromatin footprinting reveals changes in replication origin architecture induced by pre-RC assembly. Genes Dev 2015; 29:212-24. [PMID: 25593310 PMCID: PMC4298139 DOI: 10.1101/gad.247924.114] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Abstract
Start sites of DNA replication are marked by the origin recognition complex (ORC), which coordinates Mcm2–7 helicase loading to form the prereplicative complex (pre-RC). Belsky et al. “footprinted” nucleosomes, transcription factors, and replication proteins at multiple points during the Saccharomyces cerevisiae cell cycle. This revealed a precise ORC-dependent footprint at 269 origins in G2. A separate class of inefficient origins exhibited protein occupancy only in G1. The local chromatin environment restricts the loading of the Mcm2–7 double hexamer either upstream of or downstream from the ACS. Start sites of DNA replication are marked by the origin recognition complex (ORC), which coordinates Mcm2–7 helicase loading to form the prereplicative complex (pre-RC). Although pre-RC assembly is well characterized in vitro, the process is poorly understood within the local chromatin environment surrounding replication origins. To reveal how the chromatin architecture modulates origin selection and activation, we “footprinted” nucleosomes, transcription factors, and replication proteins at multiple points during the Saccharomyces cerevisiae cell cycle. Our nucleotide-resolution protein occupancy profiles resolved a precise ORC-dependent footprint at 269 origins in G2. A separate class of inefficient origins exhibited protein occupancy only in G1, suggesting that stable ORC chromatin association in G2 is a determinant of origin efficiency. G1 nucleosome remodeling concomitant with pre-RC assembly expanded the origin nucleosome-free region and enhanced activation efficiency. Finally, the local chromatin environment restricts the loading of the Mcm2–7 double hexamer either upstream of or downstream from the ARS consensus sequence (ACS).
Collapse
Affiliation(s)
- Jason A Belsky
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina 27710, USA; Program in Computational Biology and Bioinformatics, Duke University, Durham, North Carolina 27708, USA
| | - Heather K MacAlpine
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina 27710, USA;
| | - Yoav Lubelsky
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina 27710, USA
| | - Alexander J Hartemink
- Program in Computational Biology and Bioinformatics, Duke University, Durham, North Carolina 27708, USA; Department of Computer Science, Duke University, Durham, North Carolina 27708, USA
| | - David M MacAlpine
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina 27710, USA; Program in Computational Biology and Bioinformatics, Duke University, Durham, North Carolina 27708, USA;
| |
Collapse
|
39
|
Peng C, Luo H, Zhang X, Gao F. Recent advances in the genome-wide study of DNA replication origins in yeast. Front Microbiol 2015; 6:117. [PMID: 25745419 PMCID: PMC4333867 DOI: 10.3389/fmicb.2015.00117] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2014] [Accepted: 01/29/2015] [Indexed: 11/13/2022] Open
Abstract
DNA replication, one of the central events in the cell cycle, is the basis of biological inheritance. In order to be duplicated, a DNA double helix must be opened at defined sites, which are called DNA replication origins (ORIs). Unlike in bacteria, where replication initiates from a single replication origin, multiple origins are utilized in the eukaryotic genomes. Among them, the ORIs in budding yeast Saccharomyces cerevisiae and the fission yeast Schizosaccharomyces pombe have been best characterized. In recent years, advances in DNA microarray and next-generation sequencing technologies have increased the number of yeast species involved in ORIs research dramatically. The ORIs in some non-conventional yeast species such as Kluyveromyces lactis and Pichia pastoris have also been genome-widely identified. Relevant databases of replication origins in yeast were constructed, then the comparative genomic analysis can be carried out. Here, we review several experimental approaches that have been used to map replication origins in yeast and some of the available web resources related to yeast ORIs. We also discuss the sequence characteristics and chromosome structures of ORIs in the four yeast species, which can be utilized to improve yeast replication origins prediction.
Collapse
Affiliation(s)
- Chong Peng
- Department of Physics, Tianjin University , Tianjin, China
| | - Hao Luo
- Department of Physics, Tianjin University , Tianjin, China
| | - Xi Zhang
- Department of Physics, Tianjin University , Tianjin, China
| | - Feng Gao
- Department of Physics, Tianjin University , Tianjin, China ; Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University , Tianjin, China ; SynBio Research Platform, Collaborative Innovation Center of Chemical Science and Engineering , Tianjin, China
| |
Collapse
|
40
|
Thierry A, Khanna V, Créno S, Lafontaine I, Ma L, Bouchier C, Dujon B. Macrotene chromosomes provide insights to a new mechanism of high-order gene amplification in eukaryotes. Nat Commun 2015; 6:6154. [PMID: 25635677 PMCID: PMC4317496 DOI: 10.1038/ncomms7154] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2014] [Accepted: 12/15/2014] [Indexed: 12/30/2022] Open
Abstract
Copy number variation of chromosomal segments is now recognized as a major source of genetic polymorphism within natural populations of eukaryotes, as well as a possible cause of genetic diseases in humans, including cancer, but its molecular bases remain incompletely understood. In the baker's yeast Saccharomyces cerevisiae, a variety of low-order amplifications (segmental duplications) were observed after adaptation to limiting environmental conditions or recovery from gene dosage imbalance, and interpreted in terms of replication-based mechanisms associated or not with homologous recombination. Here we show the emergence of novel high-order amplification structures, with corresponding overexpression of embedded genes, during evolution under favourable growth conditions of severely unfit yeast cells bearing genetically disabled genomes. Such events form massively extended chromosomes, which we propose to call macrotene, whose characteristics suggest the products of intrachromosomal rolling-circle type of replication structures, probably initiated by increased accidental template switches under important cellular stress conditions.
Collapse
Affiliation(s)
- Agnès Thierry
- Institut Pasteur, Unité de Génétique moléculaire des levures, CNRS UMR3525, Sorbonne Universités, UPMC, Univ. Paris 06 UFR927, 25, rue du Docteur Roux, F-75724 Paris, France
| | - Varun Khanna
- Institut Pasteur, Unité de Génétique moléculaire des levures, CNRS UMR3525, Sorbonne Universités, UPMC, Univ. Paris 06 UFR927, 25, rue du Docteur Roux, F-75724 Paris, France
| | - Sophie Créno
- Institut Pasteur, Genomic platform, 28, rue du Docteur Roux, F-75724 Paris, France
| | - Ingrid Lafontaine
- Institut Pasteur, Unité de Génétique moléculaire des levures, CNRS UMR3525, Sorbonne Universités, UPMC, Univ. Paris 06 UFR927, 25, rue du Docteur Roux, F-75724 Paris, France
| | - Laurence Ma
- Institut Pasteur, Genomic platform, 28, rue du Docteur Roux, F-75724 Paris, France
| | - Christiane Bouchier
- Institut Pasteur, Genomic platform, 28, rue du Docteur Roux, F-75724 Paris, France
| | - Bernard Dujon
- Institut Pasteur, Unité de Génétique moléculaire des levures, CNRS UMR3525, Sorbonne Universités, UPMC, Univ. Paris 06 UFR927, 25, rue du Docteur Roux, F-75724 Paris, France
| |
Collapse
|
41
|
Hoffman EA, McCulley A, Haarer B, Arnak R, Feng W. Break-seq reveals hydroxyurea-induced chromosome fragility as a result of unscheduled conflict between DNA replication and transcription. Genome Res 2015; 25:402-12. [PMID: 25609572 PMCID: PMC4352882 DOI: 10.1101/gr.180497.114] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
We have previously demonstrated that in Saccharomyces cerevisiae replication, checkpoint inactivation via a mec1 mutation leads to chromosome breakage at replication forks initiated from virtually all origins after transient exposure to hydroxyurea (HU), an inhibitor of ribonucleotide reductase. Here we sought to determine whether all replication forks containing single-stranded DNA gaps have equal probability of producing double-strand breaks (DSBs) when cells attempt to recover from HU exposure. We devised a new methodology, Break-seq, that combines our previously described DSB labeling with next generation sequencing to map chromosome breaks with improved sensitivity and resolution. We show that DSBs preferentially occur at genes transcriptionally induced by HU. Notably, different subsets of the HU-induced genes produced DSBs in MEC1 and mec1 cells as replication forks traversed a greater distance in MEC1 cells than in mec1 cells during recovery from HU. Specifically, while MEC1 cells exhibited chromosome breakage at stress-response transcription factors, mec1 cells predominantly suffered chromosome breakage at transporter genes, many of which are the substrates of those transcription factors. We propose that HU-induced chromosome fragility arises at higher frequency near HU-induced genes as a result of destabilized replication forks encountering transcription factor binding and/or the act of transcription. We further propose that replication inhibitors can induce unscheduled encounters between replication and transcription and give rise to distinct patterns of chromosome fragile sites.
Collapse
Affiliation(s)
- Elizabeth A Hoffman
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York 13210, USA
| | - Andrew McCulley
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York 13210, USA
| | - Brian Haarer
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York 13210, USA
| | - Remigiusz Arnak
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York 13210, USA
| | - Wenyi Feng
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York 13210, USA
| |
Collapse
|
42
|
Abstract
The budding yeast Saccharomyces cerevisiae is a powerful model organism for studying fundamental aspects of eukaryotic cell biology. This Primer article presents a brief historical perspective on the emergence of this organism as a premier experimental system over the course of the past century. An overview of the central features of the S. cerevisiae genome, including the nature of its genetic elements and general organization, is also provided. Some of the most common experimental tools and resources available to yeast geneticists are presented in a way designed to engage and challenge undergraduate and graduate students eager to learn more about the experimental amenability of budding yeast. Finally, a discussion of several major discoveries derived from yeast studies highlights the far-reaching impact that the yeast system has had and will continue to have on our understanding of a variety of cellular processes relevant to all eukaryotes, including humans.
Collapse
|
43
|
Sridhar A, Kedziora S, Donaldson AD. At short telomeres Tel1 directs early replication and phosphorylates Rif1. PLoS Genet 2014; 10:e1004691. [PMID: 25329891 PMCID: PMC4199499 DOI: 10.1371/journal.pgen.1004691] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2013] [Accepted: 08/20/2014] [Indexed: 11/19/2022] Open
Abstract
The replication time of Saccharomyces cerevisiae telomeres responds to TG1-3 repeat length, with telomeres of normal length replicating late during S phase and short telomeres replicating early. Here we show that Tel1 kinase, which is recruited to short telomeres, specifies their early replication, because we find a tel1Δ mutant has short telomeres that nonetheless replicate late. Consistent with a role for Tel1 in driving early telomere replication, initiation at a replication origin close to an induced short telomere was reduced in tel1Δ cells, in an S phase blocked by hydroxyurea. The telomeric chromatin component Rif1 mediates late replication of normal telomeres and is a potential substrate of Tel1 phosphorylation, so we tested whether Tel1 directs early replication of short telomeres by inactivating Rif1. A strain lacking both Rif1 and Tel1 behaves like a rif1Δ mutant by replicating its telomeres early, implying that Tel1 can counteract the delaying effect of Rif1 to control telomere replication time. Proteomic analyses reveals that in yku70Δ cells that have short telomeres, Rif1 is phosphorylated at Tel1 consensus sequences (S/TQ sites), with phosphorylation of Serine-1308 being completely dependent on Tel1. Replication timing analysis of a strain mutated at these phosphorylation sites, however, suggested that Tel1-mediated phosphorylation of Rif1 is not the sole mechanism of replication timing control at telomeres. Overall, our results reveal two new functions of Tel1 at shortened telomeres: phosphorylation of Rif1, and specification of early replication by counteracting the Rif1-mediated delay in initiation at nearby replication origins.
Collapse
Affiliation(s)
- Akila Sridhar
- Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen, Scotland, United Kingdom
| | - Sylwia Kedziora
- Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen, Scotland, United Kingdom
| | - Anne D. Donaldson
- Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen, Scotland, United Kingdom
- * E-mail:
| |
Collapse
|
44
|
Gispan A, Carmi M, Barkai N. Checkpoint-independent scaling of the Saccharomyces cerevisiae DNA replication program. BMC Biol 2014; 12:79. [PMID: 25288172 PMCID: PMC4218987 DOI: 10.1186/s12915-014-0079-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2014] [Accepted: 09/18/2014] [Indexed: 12/22/2022] Open
Abstract
Background In budding yeast, perturbations that prolong S phase lead to a proportionate delay in the activation times of most origins. The DNA replication checkpoint was implicated in this scaling phenotype, as an intact checkpoint was shown to be required for the delayed activation of late origins in response to hydroxyurea treatment. In support of that, scaling is lost in cells deleted of mrc1, a mediator of the replication checkpoint signal. Mrc1p, however, also plays a role in normal replication. Results To examine whether the replication checkpoint is required for scaling the replication profile with S phase duration we measured the genome-wide replication profile of different MRC1 alleles that separate its checkpoint function from its role in normal replication, and further analyzed the replication profiles of S phase mutants that are checkpoint deficient. We found that the checkpoint is not required for scaling; rather the unique replication phenotype of mrc1 deleted cells is attributed to the role of Mrc1 in normal replication. This is further supported by the replication profiles of tof1Δ which functions together with Mrc1p in normal replication, and by the distinct replication profiles of specific POL2 alleles which differ in their interaction with Mrc1p. Conclusions We suggest that the slow fork progression in mrc1 deleted cells reduces the likelihood of passive replication leading to the activation of origins that remain mostly dormant in wild-type cells. Electronic supplementary material The online version of this article (doi:10.1186/s12915-014-0079-z) contains supplementary material, which is available to authorized users.
Collapse
|
45
|
Bryan DS, Ransom M, Adane B, York K, Hesselberth JR. High resolution mapping of modified DNA nucleobases using excision repair enzymes. Genome Res 2014; 24:1534-42. [PMID: 25015380 PMCID: PMC4158761 DOI: 10.1101/gr.174052.114] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Accepted: 07/08/2014] [Indexed: 12/20/2022]
Abstract
The incorporation and creation of modified nucleobases in DNA have profound effects on genome function. We describe methods for mapping positions and local content of modified DNA nucleobases in genomic DNA. We combined in vitro nucleobase excision with massively parallel DNA sequencing (Excision-seq) to determine the locations of modified nucleobases in genomic DNA. We applied the Excision-seq method to map uracil in E. coli and budding yeast and discovered significant variation in uracil content, wherein uracil is excluded from the earliest and latest replicating regions of the genome, possibly driven by changes in nucleotide pool composition. We also used Excision-seq to identify sites of pyrimidine dimer formation induced by UV light exposure, where the method could distinguish between sites of cyclobutane and 6-4 photoproduct formation. These UV mapping data enabled analysis of local sequence bias around pyrimidine dimers and suggested a preference for an adenosine downstream from 6-4 photoproducts. The Excision-seq method is broadly applicable for high precision, genome-wide mapping of modified nucleobases with cognate repair enzymes.
Collapse
Affiliation(s)
- D Suzi Bryan
- Department of Biochemistry and Molecular Genetics, Program in Molecular Biology, University of Colorado School of Medicine, Aurora, Colorado 80045, USA
| | - Monica Ransom
- Department of Biochemistry and Molecular Genetics, Program in Molecular Biology, University of Colorado School of Medicine, Aurora, Colorado 80045, USA
| | - Biniam Adane
- Department of Biochemistry and Molecular Genetics, Program in Molecular Biology, University of Colorado School of Medicine, Aurora, Colorado 80045, USA
| | - Kerri York
- Department of Biochemistry and Molecular Genetics, Program in Molecular Biology, University of Colorado School of Medicine, Aurora, Colorado 80045, USA
| | - Jay R Hesselberth
- Department of Biochemistry and Molecular Genetics, Program in Molecular Biology, University of Colorado School of Medicine, Aurora, Colorado 80045, USA
| |
Collapse
|
46
|
Domain within the helicase subunit Mcm4 integrates multiple kinase signals to control DNA replication initiation and fork progression. Proc Natl Acad Sci U S A 2014; 111:E1899-908. [PMID: 24740181 DOI: 10.1073/pnas.1404063111] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Eukaryotic DNA synthesis initiates from multiple replication origins and progresses through bidirectional replication forks to ensure efficient duplication of the genome. Temporal control of initiation from origins and regulation of replication fork functions are important aspects for maintaining genome stability. Multiple kinase-signaling pathways are involved in these processes. The Dbf4-dependent Cdc7 kinase (DDK), cyclin-dependent kinase (CDK), and Mec1, the yeast Ataxia telangiectasia mutated/Ataxia telangiectasia mutated Rad3-related checkpoint regulator, all target the structurally disordered N-terminal serine/threonine-rich domain (NSD) of mini-chromosome maintenance subunit 4 (Mcm4), a subunit of the mini-chromosome maintenance (MCM) replicative helicase complex. Using whole-genome replication profile analysis and single-molecule DNA fiber analysis, we show that under replication stress the temporal pattern of origin activation and DNA replication fork progression are altered in cells with mutations within two separate segments of the Mcm4 NSD. The proximal segment of the NSD residing next to the DDK-docking domain mediates repression of late-origin firing by checkpoint signals because in its absence late origins become active despite an elevated DNA damage-checkpoint response. In contrast, the distal segment of the NSD at the N terminus plays no role in the temporal pattern of origin firing but has a strong influence on replication fork progression and on checkpoint signaling. Both fork progression and checkpoint response are regulated by the phosphorylation of the canonical CDK sites at the distal NSD. Together, our data suggest that the eukaryotic MCM helicase contains an intrinsic regulatory domain that integrates multiple signals to coordinate origin activation and replication fork progression under stress conditions.
Collapse
|
47
|
Hiraga SI, Alvino GM, Chang F, Lian HY, Sridhar A, Kubota T, Brewer BJ, Weinreich M, Raghuraman MK, Donaldson AD. Rif1 controls DNA replication by directing Protein Phosphatase 1 to reverse Cdc7-mediated phosphorylation of the MCM complex. Genes Dev 2014; 28:372-83. [PMID: 24532715 PMCID: PMC3937515 DOI: 10.1101/gad.231258.113] [Citation(s) in RCA: 165] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Initiation of eukaryotic DNA replication requires phosphorylation of the MCM complex by Dbf4-dependent kinase (DDK), composed of Cdc7 kinase and its activator, Dbf4. We report here that budding yeast Rif1 (Rap1-interacting factor 1) controls DNA replication genome-wide and describe how Rif1 opposes DDK function by directing Protein Phosphatase 1 (PP1)-mediated dephosphorylation of the MCM complex. Deleting RIF1 partially compensates for the limited DDK activity in a cdc7-1 mutant strain by allowing increased, premature phosphorylation of Mcm4. PP1 interaction motifs within the Rif1 N-terminal domain are critical for its repressive effect on replication. We confirm that Rif1 interacts with PP1 and that PP1 prevents premature Mcm4 phosphorylation. Remarkably, our results suggest that replication repression by Rif1 is itself also DDK-regulated through phosphorylation near the PP1-interacting motifs. Based on our findings, we propose that Rif1 is a novel PP1 substrate targeting subunit that counteracts DDK-mediated phosphorylation during replication. Fission yeast and mammalian Rif1 proteins have also been implicated in regulating DNA replication. Since PP1 interaction sites are evolutionarily conserved within the Rif1 sequence, it is likely that replication control by Rif1 through PP1 is a conserved mechanism.
Collapse
Affiliation(s)
- Shin-Ichiro Hiraga
- Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, United Kingdom
| | | | | | | | | | | | | | | | | | | |
Collapse
|
48
|
Baker A, Bechhoefer J. Inferring the spatiotemporal DNA replication program from noisy data. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2014; 89:032703. [PMID: 24730871 DOI: 10.1103/physreve.89.032703] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2013] [Indexed: 06/03/2023]
Abstract
We generalize a stochastic model of DNA replication to the case where replication-origin-initiation rates vary locally along the genome and with time. Using this generalized model, we address the inverse problem of inferring initiation rates from experimental data concerning replication in cell populations. Previous work based on curve fitting depended on arbitrarily chosen functional forms for the initiation rate, with free parameters that were constrained by the data. We introduce a nonparametric method of inference that is based on Gaussian process regression. The method replaces specific assumptions about the functional form of the initiation rate with more general prior expectations about the smoothness of variation of this rate, along the genome and in time. Using this inference method, we recover, with high precision, simulated replication schemes from noisy data that are typical of current experiments.
Collapse
Affiliation(s)
- A Baker
- Department of Physics, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6
| | - J Bechhoefer
- Department of Physics, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6
| |
Collapse
|
49
|
Krawczyk C, Dion V, Schär P, Fritsch O. Reversible Top1 cleavage complexes are stabilized strand-specifically at the ribosomal replication fork barrier and contribute to ribosomal DNA stability. Nucleic Acids Res 2014; 42:4985-95. [PMID: 24574527 PMCID: PMC4005688 DOI: 10.1093/nar/gku148] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Various topological constraints at the ribosomal DNA (rDNA) locus impose an extra challenge for transcription and DNA replication, generating constant torsional DNA stress. The topoisomerase Top1 is known to release such torsion by single-strand nicking and re-ligation in a process involving transient covalent Top1 cleavage complexes (Top1cc) with the nicked DNA. Here we show that Top1ccs, despite their usually transient nature, are specifically targeted to and stabilized at the ribosomal replication fork barrier (rRFB) of budding yeast, establishing a link with previously reported Top1 controlled nicks. Using ectopically engineered rRFBs, we establish that the rRFB sequence itself is sufficient for induction of DNA strand-specific and replication-independent Top1ccs. These Top1ccs accumulate only in the presence of Fob1 and Tof2, they are reversible as they are not subject to repair by Tdp1- or Mus81-dependent processes, and their presence correlates with Top1 provided rDNA stability. Notably, the targeted formation of these Top1ccs accounts for the previously reported broken replication forks at the rRFB. These findings implicate a novel and physiologically regulated mode of Top1 action, suggesting a mechanism by which Top1 is recruited to the rRFB and stabilized in a reversible Top1cc configuration to preserve the integrity of the rDNA.
Collapse
Affiliation(s)
- Claudia Krawczyk
- Department of Biomedicine, University of Basel, 4058 Basel, Switzerland and Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, 4058 Basel, Switzerland
| | | | | | | |
Collapse
|
50
|
Minimal, encapsulated proteomic-sample processing applied to copy-number estimation in eukaryotic cells. Nat Methods 2014; 11:319-24. [PMID: 24487582 DOI: 10.1038/nmeth.2834] [Citation(s) in RCA: 1166] [Impact Index Per Article: 116.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2013] [Accepted: 12/20/2013] [Indexed: 12/13/2022]
Abstract
Mass spectrometry (MS)-based proteomics typically employs multistep sample-preparation workflows that are subject to sample contamination and loss. We report an in-StageTip method for performing sample processing, from cell lysis through elution of purified peptides, in a single, enclosed volume. This robust and scalable method largely eliminates contamination or loss. Peptides can be eluted in several fractions or in one step for single-run proteome analysis. In one day, we obtained the largest proteome coverage to date for budding and fission yeast, and found that protein copy numbers in these cells were highly correlated (R(2) = 0.78). Applying the in-StageTip method to quadruplicate measurements of a human cell line, we obtained copy-number estimates for 9,667 human proteins and observed excellent quantitative reproducibility between replicates (R(2) = 0.97). The in-StageTip method is straightforward and generally applicable in biological or clinical applications.
Collapse
|