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Gnügge R, Reginato G, Cejka P, Symington LS. Sequence and chromatin features guide DNA double-strand break resection initiation. Mol Cell 2023; 83:1237-1250.e15. [PMID: 36917982 PMCID: PMC10131398 DOI: 10.1016/j.molcel.2023.02.010] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2022] [Revised: 01/09/2023] [Accepted: 02/09/2023] [Indexed: 03/14/2023]
Abstract
DNA double-strand breaks (DSBs) are cytotoxic genome lesions that must be accurately and efficiently repaired to ensure genome integrity. In yeast, the Mre11-Rad50-Xrs2 (MRX) complex nicks 5'-terminated DSB ends to initiate nucleolytic processing of DSBs for repair by homologous recombination. How MRX-DNA interactions support 5' strand-specific nicking and how nicking is influenced by the chromatin context have remained elusive. Using a deep sequencing-based assay, we mapped MRX nicks at single-nucleotide resolution next to multiple DSBs in the yeast genome. We observed that the DNA end-binding Ku70-Ku80 complex directed DSB-proximal nicks and that repetitive MRX cleavage extended the length of resection tracts. We identified a sequence motif and a DNA meltability profile that is preferentially nicked by MRX. Furthermore, we found that nucleosomes as well as transcription impeded MRX incisions. Our findings suggest that local DNA sequence and chromatin features shape the activity of this central DSB repair complex.
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Affiliation(s)
- Robert Gnügge
- Department of Microbiology & Immunology, Columbia University Irving Medical Center, New York, NY 10032, USA.
| | - Giordano Reginato
- Department of Biology, Institute of Biochemistry, Eidgenössische Technische Hochschule (ETH), 8093 Zürich, Switzerland; Institute for Research in Biomedicine, Università della Svizzera italiana (USI), Faculty of Biomedical Sciences, 6500 Bellinzona, Switzerland
| | - Petr Cejka
- Department of Biology, Institute of Biochemistry, Eidgenössische Technische Hochschule (ETH), 8093 Zürich, Switzerland; Institute for Research in Biomedicine, Università della Svizzera italiana (USI), Faculty of Biomedical Sciences, 6500 Bellinzona, Switzerland
| | - Lorraine S Symington
- Department of Microbiology & Immunology, Columbia University Irving Medical Center, New York, NY 10032, USA; Department of Genetics & Development, Columbia University Irving Medical Center, New York, NY 10032, USA.
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2
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Identification and analysis of putative tRNA genes in baculovirus genomes. Virus Res 2022; 322:198949. [PMID: 36181979 DOI: 10.1016/j.virusres.2022.198949] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2022] [Revised: 09/26/2022] [Accepted: 09/27/2022] [Indexed: 12/24/2022]
Abstract
Transfer RNAs (tRNAs) genes are both coded for and arranged along some viral genomes representing the entire virosphere and seem to play different biological functions during infection, other than transferring the correct amino acid to a growing peptide chain. Baculovirus genome description and annotation has focused mostly on protein-coding genes, microRNA, and homologous regions. Here we carried out a large-scale in silico search for putative tRNA genes in baculovirus genomes. Ninety-six of 257 baculovirus genomes analyzed was found to contain at least one putative tRNA gene. We found great diversity in primary and secondary structure, in location within the genome, in intron presence and size, and in anti-codon identity. In some cases, genes of tRNA-containing genomes were found to have a bias for the codons specified by the tRNAs present in such genomes. Moreover, analysis revealed that most of the putative tRNA genes possessed conserved motifs for tRNA type 2 promoters, including the A-box and B-box motifs with few mismatches from the eukaryotic canonical motifs. From publicly available small RNA deep sequencing datasets of baculovirus-infected insect cells, we found evidence that a putative Autographa californica multiple nucleopolyhedrovirus Gln-tRNA gene was transcribed and modified with the addition of the non-templated 3'-CCA tail found at the end of all tRNAs. Further research is needed to determine the expression and functionality of these viral tRNAs.
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3
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Maree JP, Tvardovskiy A, Ravnsborg T, Jensen ON, Rudenko G, Patterton HG. Trypanosoma brucei histones are heavily modified with combinatorial post-translational modifications and mark Pol II transcription start regions with hyperacetylated H2A. Nucleic Acids Res 2022; 50:9705-9723. [PMID: 36095123 PMCID: PMC9508842 DOI: 10.1093/nar/gkac759] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2022] [Revised: 08/09/2022] [Accepted: 08/30/2022] [Indexed: 11/12/2022] Open
Abstract
Trypanosomes diverged from the main eukaryotic lineage about 600 million years ago, and display some unusual genomic and epigenetic properties that provide valuable insight into the early processes employed by eukaryotic ancestors to regulate chromatin-mediated functions. We analysed Trypanosoma brucei core histones by high mass accuracy middle-down mass spectrometry to map core histone post-translational modifications (PTMs) and elucidate cis-histone combinatorial PTMs (cPTMs). T. brucei histones are heavily modified and display intricate cPTMs patterns, with numerous hypermodified cPTMs that could contribute to the formation of non-repressive euchromatic states. The Trypanosoma brucei H2A C-terminal tail is hyperacetylated, containing up to five acetylated lysine residues. MNase-ChIP-seq revealed a striking enrichment of hyperacetylated H2A at Pol II transcription start regions, and showed that H2A histones that are hyperacetylated in different combinations localised to different genomic regions, suggesting distinct epigenetic functions. Our genomics and proteomics data provide insight into the complex epigenetic mechanisms used by this parasite to regulate a genome that lacks the transcriptional control mechanisms found in later-branched eukaryotes. The findings further demonstrate the complexity of epigenetic mechanisms that were probably shared with the last eukaryotic common ancestor.
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Affiliation(s)
- Johannes P Maree
- Department of Biochemistry, Stellenbosch University, Stellenbosch 7600, South Africa
| | - Andrey Tvardovskiy
- Department of Biochemistry and Molecular Biology, VILLUM Center for Bioanalytical Sciences, and Center for Epigenetics, University of Southern Denmark, Odense M DK-5230, Denmark
| | - Tina Ravnsborg
- Department of Biochemistry and Molecular Biology, VILLUM Center for Bioanalytical Sciences, and Center for Epigenetics, University of Southern Denmark, Odense M DK-5230, Denmark
| | - Ole N Jensen
- Department of Biochemistry and Molecular Biology, VILLUM Center for Bioanalytical Sciences, and Center for Epigenetics, University of Southern Denmark, Odense M DK-5230, Denmark
| | - Gloria Rudenko
- Department of Life Sciences, Imperial College London, London SW7 2AZ, UK
| | - Hugh-G Patterton
- Center for Bioinformatics and Computational Biology, Stellenbosch University, Stellenbosch 7600, South Africa
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4
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Ngubo M, Reid JL, Patterton H. Distinct structural groups of histone H3 and H4 residues have divergent effects on chronological lifespan in Saccharomyces cerevisiae. PLoS One 2022; 17:e0268760. [PMID: 35622816 PMCID: PMC9140238 DOI: 10.1371/journal.pone.0268760] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Accepted: 05/06/2022] [Indexed: 11/19/2022] Open
Abstract
We have performed a comprehensive analysis of the involvement of histone H3 and H4 residues in the regulation of chronological lifespan in yeast and identify four structural groups in the nucleosome that influence lifespan. We also identify residues where substitution with an epigenetic mimic extends lifespan, providing evidence that a simple epigenetic switch, without possible additional background modifications, causes longevity. Residues where substitution result in the most pronounced lifespan extension are all on the exposed face of the nucleosome, with the exception of H3E50, which is present on the lateral surface, between two DNA gyres. Other residues that have a more modest effect on lifespan extension are concentrated at the extremities of the H3-H4 dimer, suggesting a role in stabilizing the dimer in its nucleosome frame. Residues that reduce lifespan are buried in the histone handshake motif, suggesting that these mutations destabilize the octamer structure. All residues exposed on the nucleosome disk face and that cause lifespan extension are known to interact with Sir3. We find that substitution of H4K16 and H4H18 cause Sir3 to redistribute from telomeres and silent mating loci to secondary positions, often enriched for Rap1, Abf1 or Reb1 binding sites, whereas H3E50 does not. The redistribution of Sir3 in the genome can be reproduced by an equilibrium model based on primary and secondary binding sites with different affinities for Sir3. The redistributed Sir3 cause transcriptional repression at most of the new loci, including of genes where null mutants were previously shown to extend chronological lifespan. The transcriptomic profiles of H4K16 and H4H18 mutant strains are very similar, and compatible with a DNA replication stress response. This is distinct from the transcriptomic profile of H3E50, which matches strong induction of oxidative phosphorylation. We propose that the different groups of residues are involved in binding to heterochromatin proteins, in destabilizing the association of the nucleosome DNA, disrupting binding of the H3-H4 dimer in the nucleosome, or disrupting the structural stability of the octamer, each category impacting on chronological lifespan by a different mechanism.
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Affiliation(s)
- Mzwanele Ngubo
- Centre for Bioinformatics and Computational Biology, Stellenbosch University, Stellenbosch, South Africa
| | - Jessica Laura Reid
- Department of Biochemistry, Stellenbosch University, Stellenbosch, South Africa
| | - Hugh–George Patterton
- Centre for Bioinformatics and Computational Biology, Stellenbosch University, Stellenbosch, South Africa
- Department of Biochemistry, Stellenbosch University, Stellenbosch, South Africa
- * E-mail:
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5
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Coey CT, Clark DJ. A systematic genome-wide account of binding sites for the model transcription factor Gcn4. Genome Res 2021; 32:367-377. [PMID: 34916251 PMCID: PMC8805717 DOI: 10.1101/gr.276080.121] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2021] [Accepted: 12/15/2021] [Indexed: 12/04/2022]
Abstract
Sequence-specific DNA-binding transcription factors are central to gene regulation. They are often associated with consensus binding sites that predict far more genomic sites than are bound in vivo. One explanation is that most sites are blocked by nucleosomes, such that only sites in nucleosome-depleted regulatory regions are bound. We compared the binding of the yeast transcription factor Gcn4 in vivo using published ChIP-seq data (546 sites) and in vitro, using a modified SELEX method (“G-SELEX”), which utilizes short genomic DNA fragments to quantify binding at all sites. We confirm that Gcn4 binds strongly to an AP-1-like sequence (TGACTCA) and weakly to half-sites. However, Gcn4 binds only some of the 1078 exact matches to this sequence, even in vitro. We show that there are only 166 copies of the high-affinity RTGACTCAY site (exact match) in the yeast genome, all occupied in vivo, largely independently of whether they are located in nucleosome-depleted or nucleosomal regions. Generally, RTGACTCAR/YTGACTCAY sites are bound much more weakly and YTGACTCAR sites are unbound, with biological implications for determining induction levels. We conclude that, to a first approximation, Gcn4 binding can be predicted using the high-affinity site, without reference to chromatin structure. We propose that transcription factor binding sites should be defined more precisely using quantitative data, allowing more accurate genome-wide prediction of binding sites and greater insight into gene regulation.
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Affiliation(s)
- Christopher T Coey
- National Institute of Child Health and Human Development, National Institutes of Health
| | - David J Clark
- National Institute of Child Health and Human Development, National Institutes of Health
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6
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Measuring the buffering capacity of gene silencing in Saccharomyces cerevisiae. Proc Natl Acad Sci U S A 2021; 118:2111841118. [PMID: 34857629 PMCID: PMC8670432 DOI: 10.1073/pnas.2111841118] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/16/2021] [Indexed: 11/18/2022] Open
Abstract
Gene silencing, once established, is stably maintained for several generations. Despite the high fidelity of the inheritance of the silent state, individual components of silenced chromatin are in constant flux. Models suggest that silent loci can tolerate fluctuations in Sir proteins and histone acetylation levels, but the level of tolerance is unknown. To understand the quantitative relationships between H4K16 acetylation, Sir proteins, and silencing, we developed assays to quantitatively alter a H4K16 acetylation mimic allele and Sir protein levels and measure the effects of these changes on silencing. Our data suggest that a two- to threefold change in levels of histone marks and specific Sir proteins affects the stability of the silent state of a large chromatin domain. Gene silencing in budding yeast is mediated by Sir protein binding to unacetylated nucleosomes to form a chromatin structure that inhibits transcription. Transcriptional silencing is characterized by the high-fidelity transmission of the silent state. Despite its relative stability, the constituent parts of the silent state are in constant flux, giving rise to a model that silent loci can tolerate such fluctuations without functional consequences. However, the level of tolerance is unknown, and we developed methods to measure the threshold of histone acetylation that causes the silent chromatin state to switch to the active state as well as to measure the levels of the enzymes and structural proteins necessary for silencing. We show that loss of silencing required 50 to 75% acetyl-mimic histones, though the precise levels were influenced by silencer strength and upstream activating sequence (UAS) enhancer/promoter strength. Measurements of repressor protein levels necessary for silencing showed that reducing SIR4 gene dosage two- to threefold significantly weakened silencing, though reducing the gene copy numbers for Sir2 or Sir3 to the same extent did not significantly affect silencing suggesting that Sir4 was a limiting component in gene silencing. Calculations suggest that a mere twofold reduction in the ability of acetyltransferases to acetylate nucleosomes across a large array of nucleosomes may be sufficient to generate a transcriptionally silent domain.
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7
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McKnight LE, Crandall JG, Bailey TB, Banks OGB, Orlandi KN, Truong VN, Donovan DA, Waddell GL, Wiles ET, Hansen SD, Selker EU, McKnight JN. Rapid and inexpensive preparation of genome-wide nucleosome footprints from model and non-model organisms. STAR Protoc 2021; 2:100486. [PMID: 34041500 PMCID: PMC8141940 DOI: 10.1016/j.xpro.2021.100486] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
MNase-seq (micrococcal nuclease sequencing) is used to map nucleosome positions in eukaryotic genomes to study the relationship between chromatin structure and DNA-dependent processes. Current protocols require at least two days to isolate nucleosome-protected DNA fragments. We have developed a streamlined protocol for S. cerevisiae and other fungi which takes only three hours. Modified protocols were developed for wild fungi and mammalian cells. This method for rapidly producing sequencing-ready nucleosome footprints from several organisms makes MNase-seq faster and easier, with less chemical waste. A fast way to prepare micrococcal nuclease nucleosome footprints for MNase-seq Eliminates use of phenol and chloroform and reduces the amount of cells required Adaptable for a variety of organisms
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Affiliation(s)
- Laura E McKnight
- Institute of Molecular Biology, University of Oregon, Eugene, OR 97403, USA
| | | | - Thomas B Bailey
- Institute of Molecular Biology, University of Oregon, Eugene, OR 97403, USA
| | - Orion G B Banks
- Institute of Molecular Biology, University of Oregon, Eugene, OR 97403, USA
| | - Kona N Orlandi
- Institute of Molecular Biology, University of Oregon, Eugene, OR 97403, USA
| | - Vi N Truong
- Institute of Molecular Biology, University of Oregon, Eugene, OR 97403, USA
| | - Drake A Donovan
- Institute of Molecular Biology, University of Oregon, Eugene, OR 97403, USA
| | - Grace L Waddell
- Institute of Molecular Biology, University of Oregon, Eugene, OR 97403, USA
| | - Elizabeth T Wiles
- Institute of Molecular Biology, University of Oregon, Eugene, OR 97403, USA
| | - Scott D Hansen
- Institute of Molecular Biology, University of Oregon, Eugene, OR 97403, USA
| | - Eric U Selker
- Institute of Molecular Biology, University of Oregon, Eugene, OR 97403, USA
| | - Jeffrey N McKnight
- Institute of Molecular Biology, University of Oregon, Eugene, OR 97403, USA
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8
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Guimarães AR, Correia I, Sousa I, Oliveira C, Moura G, Bezerra AR, Santos MAS. tRNAs as a Driving Force of Genome Evolution in Yeast. Front Microbiol 2021; 12:634004. [PMID: 33776966 PMCID: PMC7990762 DOI: 10.3389/fmicb.2021.634004] [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] [Received: 11/26/2020] [Accepted: 02/01/2021] [Indexed: 11/29/2022] Open
Abstract
Transfer RNAs (tRNAs) are widely known for their roles in the decoding of the linear mRNA information into amino acid sequences of proteins. They are also multifunctional platforms in the translation process and have other roles beyond translation, including sensing amino acid abundance, interacting with the general stress response machinery, and modulating cellular adaptation, survival, and death. In this mini-review, we focus on the emerging role of tRNA genes in the organization and modification of the genomic architecture of yeast and the role of tRNA misexpression and decoding infidelity in genome stability, evolution, and adaption. We discuss published work showing how quickly tRNA genes can mutate to meet novel translational demands, how tRNAs speed up genome evolution, and how tRNA genes can be sites of genomic instability. We highlight recent works showing that loss of tRNA decoding fidelity and small alterations in tRNA expression have unexpected and profound impacts on genome stability. By dissecting these recent evidence, we hope to lay the groundwork that prompts future investigations on the mechanistic interplay between tRNAs and genome modification that likely triggers genome evolution.
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Affiliation(s)
- Ana Rita Guimarães
- Department of Medical Sciences, Institute of Biomedicine - iBiMED, University of Aveiro, Aveiro, Portugal
| | - Inês Correia
- Department of Medical Sciences, Institute of Biomedicine - iBiMED, University of Aveiro, Aveiro, Portugal
| | - Inês Sousa
- Department of Medical Sciences, Institute of Biomedicine - iBiMED, University of Aveiro, Aveiro, Portugal
| | - Carla Oliveira
- Department of Medical Sciences, Institute of Biomedicine - iBiMED, University of Aveiro, Aveiro, Portugal
| | - Gabriela Moura
- Department of Medical Sciences, Institute of Biomedicine - iBiMED, University of Aveiro, Aveiro, Portugal
| | - Ana Rita Bezerra
- Department of Medical Sciences, Institute of Biomedicine - iBiMED, University of Aveiro, Aveiro, Portugal
| | - Manuel A S Santos
- Department of Medical Sciences, Institute of Biomedicine - iBiMED, University of Aveiro, Aveiro, Portugal
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Marr LT, Ocampo J, Clark DJ, Hayes JJ. Global histone protein surface accessibility in yeast indicates a uniformly loosely packed genome with canonical nucleosomes. Epigenetics Chromatin 2021; 14:5. [PMID: 33430969 PMCID: PMC7802155 DOI: 10.1186/s13072-020-00381-5] [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] [Received: 09/01/2020] [Accepted: 12/28/2020] [Indexed: 01/09/2023] Open
Abstract
Background The vast majority of methods available to characterize genome-wide chromatin structure exploit differences in DNA accessibility to nucleases or chemical crosslinking. We developed a novel method to gauge genome-wide accessibility of histone protein surfaces within nucleosomes by assessing reactivity of engineered cysteine residues with a thiol-specific reagent, biotin-maleimide (BM). Results Yeast nuclei were obtained from cells expressing the histone mutant H2B S116C, in which a cysteine resides near the center of the external flat protein surface of the nucleosome. BM modification revealed that nucleosomes are generally equivalently accessible throughout the S. cerevisiae genome, including heterochromatic regions, suggesting limited, higher-order chromatin structures in which this surface is obstructed by tight nucleosome packing. However, we find that nucleosomes within 500 bp of transcription start sites exhibit the greatest range of accessibility, which correlates with the density of chromatin remodelers. Interestingly, accessibility is not well correlated with RNA polymerase density and thus the level of gene expression. We also investigated the accessibility of cysteine mutations designed to detect exposure of histone surfaces internal to the nucleosome thought to be accessible in actively transcribed genes: H3 102, is at the H2A–H2B dimer/H3–H4 tetramer interface, and H3 A110C, resides at the H3–H3 interface. However, in contrast to the external surface site, we find that neither of these internal sites were found to be appreciably exposed. Conclusions Overall, our finding that nucleosomes surfaces within S. cerevisiae chromatin are equivalently accessible genome-wide is consistent with a globally uncompacted chromatin structure lacking substantial higher-order organization. However, we find modest differences in accessibility that correlate with chromatin remodelers but not transcription, suggesting chromatin poised for transcription is more accessible than actively transcribed or intergenic regions. In contrast, we find that two internal sites remain inaccessible, suggesting that such non-canonical nucleosome species generated during transcription are rapidly and efficiently converted to canonical nucleosome structure and thus not widely present in native chromatin.
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Affiliation(s)
- Luke T Marr
- Department of Biochemistry and Biophysics, University of Rochester Medical Center, Rochester, NY, 14642, USA
| | - Josefina Ocampo
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres" (INGEBI-CONICET), C1428ADN, Buenos Aires, Argentina
| | - David J Clark
- Division of Developmental Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD, 20892, USA
| | - Jeffrey J Hayes
- Department of Biochemistry and Biophysics, University of Rochester Medical Center, Rochester, NY, 14642, USA.
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10
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Reca S, Galello F, Ojeda L, Pautasso C, Cañonero L, Moreno S, Portela P, Rossi S. Chromatin remodeling and transcription of the TPK1 subunit of PKA during stress in Saccharomyces cerevisiae. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2020; 1863:194599. [DOI: 10.1016/j.bbagrm.2020.194599] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Revised: 06/22/2020] [Accepted: 06/22/2020] [Indexed: 01/10/2023]
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Interplay among ATP-Dependent Chromatin Remodelers Determines Chromatin Organisation in Yeast. BIOLOGY 2020; 9:biology9080190. [PMID: 32722483 PMCID: PMC7466152 DOI: 10.3390/biology9080190] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/27/2020] [Revised: 07/15/2020] [Accepted: 07/21/2020] [Indexed: 02/06/2023]
Abstract
Cellular DNA is packaged into chromatin, which is composed of regularly-spaced nucleosomes with occasional gaps corresponding to active regulatory elements, such as promoters and enhancers, called nucleosome-depleted regions (NDRs). This chromatin organisation is primarily determined by the activities of a set of ATP-dependent remodeling enzymes that are capable of moving nucleosomes along DNA, or of evicting nucleosomes altogether. In yeast, the nucleosome-spacing enzymes are ISW1 (Imitation SWitch protein 1), Chromodomain-Helicase-DNA-binding (CHD)1, ISW2 (Imitation SWitch protein 2) and INOsitol-requiring 80 (INO80); the nucleosome eviction enzymes are the SWItching/Sucrose Non-Fermenting (SWI/SNF) family, the Remodeling the Structure of Chromatin (RSC) complexes and INO80. We discuss the contributions of each set of enzymes to chromatin organisation. ISW1 and CHD1 are the major spacing enzymes; loss of both enzymes results in major chromatin disruption, partly due to the appearance of close-packed di-nucleosomes. ISW1 and CHD1 compete to set nucleosome spacing on most genes. ISW1 is dominant, setting wild type spacing, whereas CHD1 sets short spacing and may dominate on highly-transcribed genes. We propose that the competing remodelers regulate spacing, which in turn controls the binding of linker histone (H1) and therefore the degree of chromatin folding. Thus, genes with long spacing bind more H1, resulting in increased chromatin compaction. RSC, SWI/SNF and INO80 are involved in NDR formation, either directly by nucleosome eviction or repositioning, or indirectly by affecting the size of the complex that resides in the NDR. The nature of this complex is controversial: some suggest that it is a RSC-bound “fragile nucleosome”, whereas we propose that it is a non-histone transcription complex. In either case, this complex appears to serve as a barrier to nucleosome formation, resulting in the formation of phased nucleosomal arrays on both sides.
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12
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Q-Nuc: a bioinformatics pipeline for the quantitative analysis of nucleosomal profiles. Interdiscip Sci 2019; 12:69-81. [PMID: 31845186 DOI: 10.1007/s12539-019-00354-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2019] [Revised: 10/20/2019] [Accepted: 11/22/2019] [Indexed: 12/26/2022]
Abstract
Nucleosomal profiling is an effective method to determine the positioning and occupancy of nucleosomes, which is essential to understand their roles in genomic processes. However, the positional randomness across the genome and its relationship with nucleosome occupancy remains poorly understood. Here we present a computational method that segments the profile into nucleosomal domains and quantifies their randomness and relative occupancy level. Applying this method to published data, we find on average ~ 3-fold differences in the degree of positional randomness between regions typically considered "well-ordered", as well as an unexpected predominance of only two types of domains of positional randomness in yeast cells. Further, we find that occupancy levels between domains actually differ maximally by ~ 2-3-fold in both cells, which has not been described before. We also developed a procedure by which one can estimate the sequencing depth that is required to identify nucleosomal positions even when regional positional randomness is high. Overall, we have developed a pipeline to quantitatively characterize domain-level features of nucleosome randomness and occupancy genome-wide, enabling the identification of otherwise unknown features in nucleosomal organization.
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13
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Marr LT, Clark DJ, Hayes JJ. A method for assessing histone surface accessibility genome-wide. Methods 2019; 184:61-69. [PMID: 31830524 DOI: 10.1016/j.ymeth.2019.12.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Revised: 12/02/2019] [Accepted: 12/06/2019] [Indexed: 01/12/2023] Open
Abstract
The assembly of DNA into nucleosomes and higher order chromatin structures serves not only as a means of compaction but also organizes the genome to facilitate crucial processes such as cell division and regulation of gene expression. Chromatin structure generally limits access to DNA, with the accessibility of DNA in chromatin being regulated through post translational modification of the histone proteins as well as the activity of chromatin remodeling proteins and architectural chromatin factors. There is great interest in assessing chromatin accessibility genome-wide to identify functional elements associated with enhancers, promoters, and other discontinuities in the compacted chromatin structure associated with gene expression. As the vast majority of techniques rely upon assessment of the exposure of the underlying DNA, we describe here a general method that can be used to assess exposure of internal and external histone protein surfaces. We demonstrate the feasibility of this method, in the organism S. cerevisiae. Our method relies on substitution of residues residing on selected histone protein surfaces with cysteine, and assessment of exposure by reaction with a thiol specific reagent, biotin-maleimide. We demonstrate that modified nucleosomes can be efficiently excised from nuclei treated with the reagent via a one-step purification process. After library preparation and deep sequencing, selected nucleosomes are typically ~25-fold enriched over background signals and exhibit phasing with respect to transcription start sites in yeast that is identical to an unselected population.
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Affiliation(s)
- Luke T Marr
- Department of Biochemistry and Biophysics, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - David J Clark
- Division of Developmental Biology, Eunice Kennedy Shriver National Institute for Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Jeffrey J Hayes
- Department of Biochemistry and Biophysics, University of Rochester Medical Center, Rochester, NY 14642, USA.
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14
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tRNA Genes Affect Chromosome Structure and Function via Local Effects. Mol Cell Biol 2019; 39:MCB.00432-18. [PMID: 30718362 DOI: 10.1128/mcb.00432-18] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Accepted: 01/18/2019] [Indexed: 11/20/2022] Open
Abstract
The genome is packaged and organized in an ordered, nonrandom manner, and specific chromatin segments contact nuclear substructures to mediate this organization. tRNA genes (tDNAs) are binding sites for transcription factors and architectural proteins and are thought to play an important role in the organization of the genome. In this study, we investigate the roles of tDNAs in genomic organization and chromosome function by editing a chromosome so that it lacked any tDNAs. Surprisingly our analyses of this tDNA-less chromosome show that loss of tDNAs does not grossly affect chromatin architecture or chromosome tethering and mobility. However, loss of tDNAs affects local nucleosome positioning and the binding of SMC proteins at these loci. The absence of tDNAs also leads to changes in centromere clustering and a reduction in the frequency of long-range HML-HMR heterochromatin clustering with concomitant effects on gene silencing. We propose that the tDNAs primarily affect local chromatin structure, which results in effects on long-range chromosome architecture.
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15
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Contrasting roles of the RSC and ISW1/CHD1 chromatin remodelers in RNA polymerase II elongation and termination. Genome Res 2019; 29:407-417. [PMID: 30683752 PMCID: PMC6396426 DOI: 10.1101/gr.242032.118] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2018] [Accepted: 01/22/2019] [Indexed: 12/17/2022]
Abstract
Most yeast genes have a nucleosome-depleted region (NDR) at the promoter and an array of regularly spaced nucleosomes phased relative to the transcription start site. We have examined the interplay between RSC (a conserved essential SWI/SNF-type complex that determines NDR size) and the ISW1, CHD1, and ISW2 nucleosome spacing enzymes in chromatin organization and transcription, using isogenic strains lacking all combinations of these enzymes. The contributions of these remodelers to chromatin organization are largely combinatorial, distinct, and nonredundant, supporting a model in which the +1 nucleosome is positioned by RSC and then used as a reference nucleosome by the spacing enzymes. Defective chromatin organization correlates with altered RNA polymerase II (Pol II) distribution. RSC-depleted cells exhibit low levels of elongating Pol II and high levels of terminating Pol II, consistent with defects in both termination and initiation, suggesting that RSC facilitates both. Cells lacking both ISW1 and CHD1 show the opposite Pol II distribution, suggesting elongation and termination defects. These cells have extremely disrupted chromatin, with high levels of closely packed dinucleosomes involving the second (+2) nucleosome. We propose that ISW1 and CHD1 facilitate Pol II elongation by separating closely packed nucleosomes.
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16
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Miura O, Ogake T, Yoneyama H, Kikuchi Y, Ohyama T. A strong structural correlation between short inverted repeat sequences and the polyadenylation signal in yeast and nucleosome exclusion by these inverted repeats. Curr Genet 2018; 65:575-590. [PMID: 30498953 PMCID: PMC6420913 DOI: 10.1007/s00294-018-0907-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Revised: 11/14/2018] [Accepted: 11/15/2018] [Indexed: 11/22/2022]
Abstract
DNA sequences that read the same from 5′ to 3′ in either strand are called inverted repeat sequences or simply IRs. They are found throughout a wide variety of genomes, from prokaryotes to eukaryotes. Despite extensive research, their in vivo functions, if any, remain unclear. Using Saccharomyces cerevisiae, we performed genome-wide analyses for the distribution, occurrence frequency, sequence characteristics and relevance to chromatin structure, for the IRs that reportedly have a cruciform-forming potential. Here, we provide the first comprehensive map of these IRs in the S. cerevisiae genome. The statistically significant enrichment of the IRs was found in the close vicinity of the DNA positions corresponding to polyadenylation [poly(A)] sites and ~ 30 to ~ 60 bp downstream of start codon-coding sites (referred to as ‘start codons’). In the former, ApT- or TpA-rich IRs and A-tract- or T-tract-rich IRs are enriched, while in the latter, different IRs are enriched. Furthermore, we found a strong structural correlation between the former IRs and the poly(A) signal. In the chromatin formed on the gene end regions, the majority of the IRs causes low nucleosome occupancy. The IRs in the region ~ 30 to ~ 60 bp downstream of start codons are located in the + 1 nucleosomes. In contrast, fewer IRs are present in the adjacent region downstream of start codons. The current study suggests that the IRs play similar roles in Escherichia coli and S. cerevisiae to regulate or complete transcription at the RNA level.
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Affiliation(s)
- Osamu Miura
- Department of Biology, Faculty of Education and Integrated Arts and Sciences, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo, 162-8480, Japan
| | - Toshihiro Ogake
- Major in Integrative Bioscience and Biomedical Engineering, Graduate School of Science and Engineering, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo, 162-8480, Japan
| | - Hiroki Yoneyama
- Major in Integrative Bioscience and Biomedical Engineering, Graduate School of Science and Engineering, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo, 162-8480, Japan
| | - Yo Kikuchi
- Major in Integrative Bioscience and Biomedical Engineering, Graduate School of Science and Engineering, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo, 162-8480, Japan
| | - Takashi Ohyama
- Department of Biology, Faculty of Education and Integrated Arts and Sciences, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo, 162-8480, Japan. .,Major in Integrative Bioscience and Biomedical Engineering, Graduate School of Science and Engineering, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo, 162-8480, Japan.
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17
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Mehta GD, Ball DA, Eriksson PR, Chereji RV, Clark DJ, McNally JG, Karpova TS. Single-Molecule Analysis Reveals Linked Cycles of RSC Chromatin Remodeling and Ace1p Transcription Factor Binding in Yeast. Mol Cell 2018; 72:875-887.e9. [PMID: 30318444 DOI: 10.1016/j.molcel.2018.09.009] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Revised: 08/08/2018] [Accepted: 09/07/2018] [Indexed: 12/12/2022]
Abstract
It is unknown how the dynamic binding of transcription factors (TFs) is molecularly linked to chromatin remodeling and transcription. Using single-molecule tracking (SMT), we show that the chromatin remodeler RSC speeds up the search process of the TF Ace1p for its response elements (REs) at the CUP1 promoter. We quantified smFISH mRNA data using a gene bursting model and demonstrated that RSC regulates transcription bursts of CUP1 only by modulating TF occupancy but does not affect initiation and elongation rates. We show by SMT that RSC binds to activated promoters transiently, and based on MNase-seq data, that RSC does not affect the nucleosomal occupancy at CUP1. Therefore, transient binding of Ace1p and rapid bursts of transcription at CUP1 may be dependent on short repetitive cycles of nucleosome mobilization. This type of regulation reduces the transcriptional noise and ensures a homogeneous response of the cell population to heavy metal stress.
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Affiliation(s)
- Gunjan D Mehta
- CCR/LRBGE Optical Microscopy Core, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - David A Ball
- CCR/LRBGE Optical Microscopy Core, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Peter R Eriksson
- Division of Developmental Biology, Eunice Kennedy Shriver National Institute for Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Razvan V Chereji
- Division of Developmental Biology, Eunice Kennedy Shriver National Institute for Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - David J Clark
- Division of Developmental Biology, Eunice Kennedy Shriver National Institute for Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - James G McNally
- Institute for Soft Matter and Functional Materials, Helmholtz Center Berlin, Berlin 12489, Germany
| | - Tatiana S Karpova
- CCR/LRBGE Optical Microscopy Core, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
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18
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Wedel C, Förstner KU, Derr R, Siegel TN. GT-rich promoters can drive RNA pol II transcription and deposition of H2A.Z in African trypanosomes. EMBO J 2017; 36:2581-2594. [PMID: 28701485 PMCID: PMC5579346 DOI: 10.15252/embj.201695323] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Revised: 05/30/2017] [Accepted: 05/31/2017] [Indexed: 01/25/2023] Open
Abstract
Genome‐wide transcription studies are revealing an increasing number of “dispersed promoters” that, unlike “focused promoters”, lack well‐conserved sequence motifs and tight regulation. Dispersed promoters are nevertheless marked by well‐defined chromatin structures, suggesting that specific sequence elements must exist in these unregulated promoters. Here, we have analyzed regions of transcription initiation in the eukaryotic parasite Trypanosoma brucei, in which RNA polymerase II transcription initiation occurs over broad regions without distinct promoter motifs and lacks regulation. Using a combination of site‐specific and genome‐wide assays, we identified GT‐rich promoters that can drive transcription and promote the targeted deposition of the histone variant H2A.Z in a genomic context‐dependent manner. In addition, upon mapping nucleosome occupancy at high resolution, we find nucleosome positioning to correlate with RNA pol II enrichment and gene expression, pointing to a role in RNA maturation. Nucleosome positioning may thus represent a previously unrecognized layer of gene regulation in trypanosomes. Our findings show that even highly dispersed, unregulated promoters contain specific DNA elements that are able to induce transcription and changes in chromatin structure.
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Affiliation(s)
- Carolin Wedel
- Research Center for Infectious Diseases, Universität Würzburg, Würzburg, Germany
| | | | - Ramona Derr
- Research Center for Infectious Diseases, Universität Würzburg, Würzburg, Germany
| | - T Nicolai Siegel
- Research Center for Infectious Diseases, Universität Würzburg, Würzburg, Germany .,Department of Veterinary Sciences, Experimental Parasitology, Ludwig-Maximilians-Universität München, München, Germany.,Biomedical Center Munich, Physiological Chemistry, Ludwig-Maximilians-Universität München, Planegg-Martinsried, Germany
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19
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Abstract
Eukaryotic DNA is packaged into regularly spaced nucleosomes, resembling beads on a string. Each bead contains ∼147 bp wrapped around a core histone octamer. Linker histone (H1) binds to the linker DNA to drive chromatin folding. Micrococcal nuclease (MNase) digestion studies reveal 2 mono-nucleosomal intermediates: the core particle (∼147 bp) and the chromatosome (∼160 bp; a core particle with additional DNA protected by H1). We have recently developed an improved method for mapping nucleosomes, using exonuclease III to remove residual linker (MNase-Exo-seq). (1) We discovered 2 new intermediate particles corresponding to core particles with ∼7 bp of linker protruding from one side (∼154 bp) or both sides (∼161 bp), which are formed in the absence of H1. We propose that these "proto-chromatosomes" are stabilized by core histone-DNA contacts in the linker, ∼7 bp from the nucleosome boundaries. These contacts may determine the topography of the H1 binding site.
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Affiliation(s)
- Josefina Ocampo
- a Division of Developmental Biology, Eunice Kennedy Shriver National Institute for Child Health and Human Development, National Institutes of Health , Bethesda , MD , USA
| | - Feng Cui
- b Thomas H. Gosnell School of Life Sciences, Rochester Institute of Technology , Rochester , NY , USA
| | - Victor B Zhurkin
- c National Cancer Institute, National Institutes of Health , Bethesda , MD , USA
| | - David J Clark
- a Division of Developmental Biology, Eunice Kennedy Shriver National Institute for Child Health and Human Development, National Institutes of Health , Bethesda , MD , USA
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20
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Azmi IF, Watanabe S, Maloney MF, Kang S, Belsky JA, MacAlpine DM, Peterson CL, Bell SP. Nucleosomes influence multiple steps during replication initiation. eLife 2017; 6. [PMID: 28322723 PMCID: PMC5400510 DOI: 10.7554/elife.22512] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2016] [Accepted: 03/20/2017] [Indexed: 12/20/2022] Open
Abstract
Eukaryotic replication origin licensing, activation and timing are influenced by chromatin but a mechanistic understanding is lacking. Using reconstituted nucleosomal DNA replication assays, we assessed the impact of nucleosomes on replication initiation. To generate distinct nucleosomal landscapes, different chromatin-remodeling enzymes (CREs) were used to remodel nucleosomes on origin-DNA templates. Nucleosomal organization influenced two steps of replication initiation: origin licensing and helicase activation. Origin licensing assays showed that local nucleosome positioning enhanced origin specificity and modulated helicase loading by influencing ORC DNA binding. Interestingly, SWI/SNF- and RSC-remodeled nucleosomes were permissive for origin licensing but showed reduced helicase activation. Specific CREs rescued replication of these templates if added prior to helicase activation, indicating a permissive chromatin state must be established during origin licensing to allow efficient origin activation. Our studies show nucleosomes directly modulate origin licensing and activation through distinct mechanisms and provide insights into the regulation of replication initiation by chromatin.
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Affiliation(s)
- Ishara F Azmi
- Department of Biology, Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, United States
| | - Shinya Watanabe
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, United States
| | - Michael F Maloney
- Department of Biology, Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, United States
| | - Sukhyun Kang
- Department of Biology, Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, United States.,Center for Genomic Integrity, Institute for Basic Science, Ulsan, South Korea
| | - Jason A Belsky
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, United States.,Program in Computational Biology and Bioinformatics, Duke University, Durham, United States
| | - David M MacAlpine
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, United States
| | - Craig L Peterson
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, United States
| | - Stephen P Bell
- Department of Biology, Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, United States
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21
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Maree JP, Povelones ML, Clark DJ, Rudenko G, Patterton HG. Well-positioned nucleosomes punctuate polycistronic pol II transcription units and flank silent VSG gene arrays in Trypanosoma brucei. Epigenetics Chromatin 2017; 10:14. [PMID: 28344657 PMCID: PMC5359979 DOI: 10.1186/s13072-017-0121-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2017] [Accepted: 03/14/2017] [Indexed: 12/18/2022] Open
Abstract
Background The compaction of DNA in chromatin in eukaryotes allowed the expansion of genome size and coincided with significant evolutionary diversification. However, chromatin generally represses DNA function, and mechanisms coevolved to regulate chromatin structure and its impact on DNA. This included the selection of specific nucleosome positions to modulate accessibility to the DNA molecule. Trypanosoma brucei, a member of the Excavates supergroup, falls in an ancient evolutionary branch of eukaryotes and provides valuable insight into the organization of chromatin in early genomes. Results We have mapped nucleosome positions in T. brucei and identified important differences compared to other eukaryotes: The RNA polymerase II initiation regions in T. brucei do not exhibit pronounced nucleosome depletion, and show little evidence for defined −1 and +1 nucleosomes. In contrast, a well-positioned nucleosome is present directly on the splice acceptor sites within the polycistronic transcription units. The RNA polyadenylation sites were depleted of nucleosomes, with a single well-positioned nucleosome present immediately downstream of the predicted sites. The regions flanking the silent variant surface glycoprotein (VSG) gene cassettes showed extensive arrays of well-positioned nucleosomes, which may repress cryptic transcription initiation. The silent VSG genes themselves exhibited a less regular nucleosomal pattern in both bloodstream and procyclic form trypanosomes. The DNA replication origins, when present within silent VSG gene cassettes, displayed a defined nucleosomal organization compared with replication origins in other chromosomal core regions. Conclusions Our results indicate that some organizational features of chromatin are evolutionarily ancient, and may already have been present in the last eukaryotic common ancestor. Electronic supplementary material The online version of this article (doi:10.1186/s13072-017-0121-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
| | - Megan Lindsay Povelones
- Department of Biology, Pennsylvania State University (Brandywine Campus), Media, PA 19063 USA
| | - David Johannes Clark
- Division of Developmental Biology, Eunice Kennedy Shriver National Institute for Child Health and Human Development, National Institutes of Health, Bethesda, MD USA
| | - Gloria Rudenko
- Department of Life Sciences, Imperial College London, South Kensington, London, SW7 2AZ UK
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22
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Zhang P, Du G, Zou H, Xie G, Chen J, Shi Z, Zhou J. Genome-wide mapping of nucleosome positions in Saccharomyces cerevisiae in response to different nitrogen conditions. Sci Rep 2016; 6:33970. [PMID: 27659668 PMCID: PMC5034280 DOI: 10.1038/srep33970] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2016] [Accepted: 09/06/2016] [Indexed: 12/31/2022] Open
Abstract
Well-organized chromatin is involved in a number of various transcriptional regulation and gene expression. We used genome-wide mapping of nucleosomes in response to different nitrogen conditions to determine both nucleosome profiles and gene expression events in Saccharomyces cerevisiae. Nitrogen conditions influence general nucleosome profiles and the expression of nitrogen catabolite repression (NCR) sensitive genes. The nucleosome occupancy of TATA-containing genes was higher compared to TATA-less genes. TATA-less genes in high or low nucleosome occupancy, showed a significant change in gene coding regions when shifting cells from glutamine to proline as the sole nitrogen resource. Furthermore, a correlation between the expression of nucleosome occupancy induced NCR sensitive genes or TATA containing genes in NCR sensitive genes, and nucleosome prediction were found when cells were cultured in proline or shifting from glutamine to proline as the sole nitrogen source compared to glutamine. These results also showed that variation of nucleosome occupancy accompany with chromatin-dependent transcription factor could influence the expression of a series of genes involved in the specific regulation of nitrogen utilization.
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Affiliation(s)
- Peng Zhang
- Key Laboratory of Industrial Biotechnology, Ministry of Education and School of Biotechnology, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China
| | - Guocheng Du
- Key Laboratory of Industrial Biotechnology, Ministry of Education and School of Biotechnology, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China
| | - Huijun Zou
- Zhejiang Guyuelongshan Shaoxing Wine Company, 13 Yangjiang Road, Shaoxing, Zhejiang, China
| | - Guangfa Xie
- Zhejiang Guyuelongshan Shaoxing Wine Company, 13 Yangjiang Road, Shaoxing, Zhejiang, China
| | - Jian Chen
- Key Laboratory of Industrial Biotechnology, Ministry of Education and School of Biotechnology, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China
| | - Zhongping Shi
- Key Laboratory of Industrial Biotechnology, Ministry of Education and School of Biotechnology, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China
| | - Jingwen Zhou
- Key Laboratory of Industrial Biotechnology, Ministry of Education and School of Biotechnology, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China
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23
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Chereji RV, Kan TW, Grudniewska MK, Romashchenko AV, Berezikov E, Zhimulev IF, Guryev V, Morozov AV, Moshkin YM. Genome-wide profiling of nucleosome sensitivity and chromatin accessibility in Drosophila melanogaster. Nucleic Acids Res 2016; 44:1036-51. [PMID: 26429969 PMCID: PMC4756854 DOI: 10.1093/nar/gkv978] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2015] [Revised: 08/27/2015] [Accepted: 09/16/2015] [Indexed: 01/09/2023] Open
Abstract
Nucleosomal DNA is thought to be generally inaccessible to DNA-binding factors, such as micrococcal nuclease (MNase). Here, we digest Drosophila chromatin with high and low concentrations of MNase to reveal two distinct nucleosome types: MNase-sensitive and MNase-resistant. MNase-resistant nucleosomes assemble on sequences depleted of A/T and enriched in G/C-containing dinucleotides, whereas MNase-sensitive nucleosomes form on A/T-rich sequences found at transcription start and termination sites, enhancers and DNase I hypersensitive sites. Estimates of nucleosome formation energies indicate that MNase-sensitive nucleosomes tend to be less stable than MNase-resistant ones. Strikingly, a decrease in cell growth temperature of about 10°C makes MNase-sensitive nucleosomes less accessible, suggesting that observed variations in MNase sensitivity are related to either thermal fluctuations of chromatin fibers or the activity of enzymatic machinery. In the vicinity of active genes and DNase I hypersensitive sites nucleosomes are organized into periodic arrays, likely due to 'phasing' off potential barriers formed by DNA-bound factors or by nucleosomes anchored to their positions through external interactions. The latter idea is substantiated by our biophysical model of nucleosome positioning and energetics, which predicts that nucleosomes immediately downstream of transcription start sites are anchored and recapitulates nucleosome phasing at active genes significantly better than sequence-dependent models.
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Affiliation(s)
- Răzvan V Chereji
- Program in Genomics of Differentiation, Eunice Kennedy Shriver National Institute for Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Tsung-Wai Kan
- Department of Biochemistry, Erasmus Medical Center, P.O. Box 2040, 3000 CA Rotterdam, The Netherlands
| | - Magda K Grudniewska
- European Research Institute for the Biology of Ageing, University of Groningen, University Medical Center Groningen, Groningen, 9713AD, The Netherlands
| | | | - Eugene Berezikov
- European Research Institute for the Biology of Ageing, University of Groningen, University Medical Center Groningen, Groningen, 9713AD, The Netherlands
| | - Igor F Zhimulev
- Institute of Molecular and Cellular Biology, Siberian Branch of RAS, Novosibirsk 630090, Russia
| | - Victor Guryev
- European Research Institute for the Biology of Ageing, University of Groningen, University Medical Center Groningen, Groningen, 9713AD, The Netherlands
| | - Alexandre V Morozov
- Department of Physics and Astronomy and BioMaPS Institute for Quantitative Biology, Rutgers University, Piscataway, NJ 08854, USA
| | - Yuri M Moshkin
- Department of Biochemistry, Erasmus Medical Center, P.O. Box 2040, 3000 CA Rotterdam, The Netherlands Institute of Cytology and Genetics, Siberian Branch of RAS, Novosibirsk 630090, Russia Institute of Molecular and Cellular Biology, Siberian Branch of RAS, Novosibirsk 630090, Russia
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24
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Ocampo J, Chereji RV, Eriksson PR, Clark DJ. The ISW1 and CHD1 ATP-dependent chromatin remodelers compete to set nucleosome spacing in vivo. Nucleic Acids Res 2016; 44:4625-35. [PMID: 26861626 PMCID: PMC4889916 DOI: 10.1093/nar/gkw068] [Citation(s) in RCA: 87] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2015] [Accepted: 01/28/2016] [Indexed: 12/17/2022] Open
Abstract
Adenosine triphosphate-dependent chromatin remodeling machines play a central role in gene regulation by manipulating chromatin structure. Most genes have a nucleosome-depleted region at the promoter and an array of regularly spaced nucleosomes phased relative to the transcription start site. In vitro, the three known yeast nucleosome spacing enzymes (CHD1, ISW1 and ISW2) form arrays with different spacing. We used genome-wide nucleosome sequencing to determine whether these enzymes space nucleosomes differently in vivo We find that CHD1 and ISW1 compete to set the spacing on most genes, such that CHD1 dominates genes with shorter spacing and ISW1 dominates genes with longer spacing. In contrast, ISW2 plays a minor role, limited to transcriptionally inactive genes. Heavily transcribed genes show weak phasing and extreme spacing, either very short or very long, and are depleted of linker histone (H1). Genes with longer spacing are enriched in H1, which directs chromatin folding. We propose that CHD1 directs short spacing, resulting in eviction of H1 and chromatin unfolding, whereas ISW1 directs longer spacing, allowing H1 to bind and condense the chromatin. Thus, competition between the two remodelers to set the spacing on each gene may result in a highly dynamic chromatin structure.
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Affiliation(s)
- Josefina Ocampo
- Division of Developmental Biology, Eunice Kennedy Shriver National Institute for Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Răzvan V Chereji
- Division of Developmental Biology, Eunice Kennedy Shriver National Institute for Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Peter R Eriksson
- Division of Developmental Biology, Eunice Kennedy Shriver National Institute for Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - David J Clark
- Division of Developmental Biology, Eunice Kennedy Shriver National Institute for Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
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25
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Qiu H, Chereji RV, Hu C, Cole HA, Rawal Y, Clark DJ, Hinnebusch AG. Genome-wide cooperation by HAT Gcn5, remodeler SWI/SNF, and chaperone Ydj1 in promoter nucleosome eviction and transcriptional activation. Genome Res 2015; 26:211-25. [PMID: 26602697 PMCID: PMC4728374 DOI: 10.1101/gr.196337.115] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2015] [Accepted: 11/18/2015] [Indexed: 12/27/2022]
Abstract
Chaperones, nucleosome remodeling complexes, and histone acetyltransferases have been implicated in nucleosome disassembly at promoters of particular yeast genes, but whether these cofactors function ubiquitously, as well as the impact of nucleosome eviction on transcription genome-wide, is poorly understood. We used chromatin immunoprecipitation of histone H3 and RNA polymerase II (Pol II) in mutants lacking single or multiple cofactors to address these issues for about 200 genes belonging to the Gcn4 transcriptome, of which about 70 exhibit marked reductions in H3 promoter occupancy on induction by amino acid starvation. Examining four target genes in a panel of mutants indicated that SWI/SNF, Gcn5, the Hsp70 cochaperone Ydj1, and chromatin-associated factor Yta7 are required downstream from Gcn4 binding, whereas Asf1/Rtt109, Nap1, RSC, and H2AZ are dispensable for robust H3 eviction in otherwise wild-type cells. Using ChIP-seq to interrogate all 70 exemplar genes in single, double, and triple mutants implicated Gcn5, Snf2, and Ydj1 in H3 eviction at most, but not all, Gcn4 target promoters, with Gcn5 generally playing the greatest role and Ydj1 the least. Remarkably, these three cofactors cooperate similarly in H3 eviction at virtually all yeast promoters. Defective H3 eviction in cofactor mutants was coupled with reduced Pol II occupancies for the Gcn4 transcriptome and the most highly expressed uninduced genes, but the relative Pol II levels at most genes were unaffected or even elevated. These findings indicate that nucleosome eviction is crucial for robust transcription of highly expressed genes but that other steps in gene activation are more rate-limiting for most other yeast genes.
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Affiliation(s)
- Hongfang Qiu
- Laboratory of Gene Regulation and Development, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Răzvan V Chereji
- Program in Genomics of Differentiation, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Cuihua Hu
- Laboratory of Gene Regulation and Development, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Hope A Cole
- Program in Genomics of Differentiation, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Yashpal Rawal
- Laboratory of Gene Regulation and Development, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - David J Clark
- Program in Genomics of Differentiation, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Alan G Hinnebusch
- Laboratory of Gene Regulation and Development, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA
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26
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Abstract
Nucleosome positioning is an important process required for proper genome packing and its accessibility to execute the genetic program in a cell-specific, timely manner. In the recent years hundreds of papers have been devoted to the bioinformatics, physics and biology of nucleosome positioning. The purpose of this review is to cover a practical aspect of this field, namely, to provide a guide to the multitude of nucleosome positioning resources available online. These include almost 300 experimental datasets of genome-wide nucleosome occupancy profiles determined in different cell types and more than 40 computational tools for the analysis of experimental nucleosome positioning data and prediction of intrinsic nucleosome formation probabilities from the DNA sequence. A manually curated, up to date list of these resources will be maintained at http://generegulation.info.
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27
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Cole HA, Cui F, Ocampo J, Burke TL, Nikitina T, Nagarajavel V, Kotomura N, Zhurkin VB, Clark DJ. Novel nucleosomal particles containing core histones and linker DNA but no histone H1. Nucleic Acids Res 2015; 44:573-81. [PMID: 26400169 PMCID: PMC4737182 DOI: 10.1093/nar/gkv943] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2015] [Accepted: 09/09/2015] [Indexed: 11/12/2022] Open
Abstract
Eukaryotic chromosomal DNA is assembled into regularly spaced nucleosomes, which play a central role in gene regulation by determining accessibility of control regions. The nucleosome contains ∼147 bp of DNA wrapped ∼1.7 times around a central core histone octamer. The linker histone, H1, binds both to the nucleosome, sealing the DNA coils, and to the linker DNA between nucleosomes, directing chromatin folding. Micrococcal nuclease (MNase) digests the linker to yield the chromatosome, containing H1 and ∼160 bp, and then converts it to a core particle, containing ∼147 bp and no H1. Sequencing of nucleosomal DNA obtained after MNase digestion (MNase-seq) generates genome-wide nucleosome maps that are important for understanding gene regulation. We present an improved MNase-seq method involving simultaneous digestion with exonuclease III, which removes linker DNA. Remarkably, we discovered two novel intermediate particles containing 154 or 161 bp, corresponding to 7 bp protruding from one or both sides of the nucleosome core. These particles are detected in yeast lacking H1 and in H1-depleted mouse chromatin. They can be reconstituted in vitro using purified core histones and DNA. We propose that these ‘proto-chromatosomes’ are fundamental chromatin subunits, which include the H1 binding site and influence nucleosome spacing independently of H1.
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Affiliation(s)
- Hope A Cole
- Program in Genomics of Differentiation, Eunice Kennedy Shriver National Institute for Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Feng Cui
- Thomas H. Gosnell School of Life Sciences, Rochester Institute of Technology, Rochester, NY, USA
| | - Josefina Ocampo
- Program in Genomics of Differentiation, Eunice Kennedy Shriver National Institute for Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Tara L Burke
- Program in Genomics of Differentiation, Eunice Kennedy Shriver National Institute for Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Tatiana Nikitina
- National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - V Nagarajavel
- Program in Genomics of Differentiation, Eunice Kennedy Shriver National Institute for Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Naoe Kotomura
- Program in Genomics of Differentiation, Eunice Kennedy Shriver National Institute for Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Victor B Zhurkin
- National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - David J Clark
- Program in Genomics of Differentiation, Eunice Kennedy Shriver National Institute for Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
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Nucleosome positioning in yeasts: methods, maps, and mechanisms. Chromosoma 2014; 124:131-51. [PMID: 25529773 DOI: 10.1007/s00412-014-0501-x] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2014] [Revised: 12/02/2014] [Accepted: 12/03/2014] [Indexed: 01/23/2023]
Abstract
Eukaryotic nuclear DNA is packaged into nucleosomes. During the past decade, genome-wide nucleosome mapping across species revealed the high degree of order in nucleosome positioning. There is a conserved stereotypical nucleosome organization around transcription start sites (TSSs) with a nucleosome-depleted region (NDR) upstream of the TSS and a TSS-aligned regular array of evenly spaced nucleosomes downstream over the gene body. As nucleosomes largely impede access to DNA and thereby provide an important level of genome regulation, it is of general interest to understand the mechanisms generating nucleosome positioning and especially the stereotypical NDR-array pattern. We focus here on the most advanced models, unicellular yeasts, and review the progress in mapping nucleosomes and which nucleosome positioning mechanisms are discussed. There are four mechanistic aspects: How are NDRs generated? How are individual nucleosomes positioned, especially those flanking the NDRs? How are nucleosomes evenly spaced leading to regular arrays? How are regular arrays aligned at TSSs? The main candidates for nucleosome positioning determinants are intrinsic DNA binding preferences of the histone octamer, specific DNA binding factors, nucleosome remodeling enzymes, transcription, and statistical positioning. We summarize the state of the art in an integrative model where nucleosomes are positioned by a combination of all these candidate determinants. We highlight the predominance of active mechanisms involving nucleosome remodeling enzymes which may be recruited by DNA binding factors and the transcription machinery. While this mechanistic framework emerged clearly during recent years, the involved factors and their mechanisms are still poorly understood and require future efforts combining in vivo and in vitro approaches.
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29
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Cole HA, Ocampo J, Iben JR, Chereji RV, Clark DJ. Heavy transcription of yeast genes correlates with differential loss of histone H2B relative to H4 and queued RNA polymerases. Nucleic Acids Res 2014; 42:12512-22. [PMID: 25348398 PMCID: PMC4227747 DOI: 10.1093/nar/gku1013] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Eukaryotic chromatin is composed of nucleosomes, which contain nearly two coils of DNA wrapped around a central histone octamer. The octamer contains an H3-H4 tetramer and two H2A-H2B dimers. Gene activation is associated with chromatin disruption: a wider nucleosome-depleted region (NDR) at the promoter and reduced nucleosome occupancy over the coding region. Here, we examine the nature of disrupted chromatin after induction, using MNase-seq to map nucleosomes and subnucleosomes, and a refined high-resolution ChIP-seq method to map H4, H2B and RNA polymerase II (Pol II) genome-wide. Over coding regions, induced genes show a differential loss of H2B relative to H4, which correlates with Pol II density and the appearance of subnucleosomes. After induction, Pol II is surprisingly low at the promoter, but accumulates on the gene and downstream of the termination site, implying that dissociation is very slow. Thus, induction-dependent chromatin disruption reflects both eviction of H2A-H2B dimers and the presence of queued Pol II elongation complexes. We propose that slow Pol II dissociation after transcription is a major factor in chromatin disruption and that it may be of critical importance in gene regulation.
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Affiliation(s)
- Hope A Cole
- Program in Genomics of Differentiation, Eunice Kennedy Shriver National Institute for Child Health and Human Development, National Institutes of Health, Bethesda 20892, MD, USA
| | - Josefina Ocampo
- Program in Genomics of Differentiation, Eunice Kennedy Shriver National Institute for Child Health and Human Development, National Institutes of Health, Bethesda 20892, MD, USA
| | - James R Iben
- Program in Genomics of Differentiation, Eunice Kennedy Shriver National Institute for Child Health and Human Development, National Institutes of Health, Bethesda 20892, MD, USA
| | - Răzvan V Chereji
- Program in Genomics of Differentiation, Eunice Kennedy Shriver National Institute for Child Health and Human Development, National Institutes of Health, Bethesda 20892, MD, USA
| | - David J Clark
- Program in Genomics of Differentiation, Eunice Kennedy Shriver National Institute for Child Health and Human Development, National Institutes of Health, Bethesda 20892, MD, USA
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30
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Ganguli D, Chereji RV, Iben JR, Cole HA, Clark DJ. RSC-dependent constructive and destructive interference between opposing arrays of phased nucleosomes in yeast. Genome Res 2014; 24:1637-49. [PMID: 25015381 PMCID: PMC4199373 DOI: 10.1101/gr.177014.114] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
RSC and SWI/SNF are related ATP-dependent chromatin remodeling machines that move nucleosomes, regulating access to DNA. We addressed their roles in nucleosome phasing relative to transcription start sites in yeast. SWI/SNF has no effect on phasing at the global level. In contrast, RSC depletion results in global nucleosome repositioning: Both upstream and downstream nucleosomal arrays shift toward the nucleosome-depleted region (NDR), with no change in spacing, resulting in a narrower and partly filled NDR. The global picture of RSC-depleted chromatin represents the average of a range of chromatin structures, with most genes showing a shift of the +1 or the -1 nucleosome into the NDR. Using RSC ChIP data reported by others, we show that RSC occupancy is highest on the coding regions of heavily transcribed genes, though not at their NDRs. We propose that RSC has a role in restoring chromatin structure after transcription. Analysis of gene pairs in different orientations demonstrates that phasing patterns reflect competition between phasing signals emanating from neighboring NDRs. These signals may be in phase, resulting in constructive interference and a regular array, or out of phase, resulting in destructive interference and fuzzy positioning. We propose a modified barrier model, in which a stable complex located at the NDR acts as a bidirectional phasing barrier. In RSC-depleted cells, this barrier has a smaller footprint, resulting in narrower NDRs. Thus, RSC plays a critical role in organizing yeast chromatin.
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Affiliation(s)
- Dwaipayan Ganguli
- Program in Genomics of Differentiation, Eunice Kennedy Shriver National Institute for Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Răzvan V Chereji
- Program in Genomics of Differentiation, Eunice Kennedy Shriver National Institute for Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - James R Iben
- Program in Genomics of Differentiation, Eunice Kennedy Shriver National Institute for Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Hope A Cole
- Program in Genomics of Differentiation, Eunice Kennedy Shriver National Institute for Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - David J Clark
- Program in Genomics of Differentiation, Eunice Kennedy Shriver National Institute for Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA
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