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Miller CLW, Warner JL, Winston F. Insights into Spt6: a histone chaperone that functions in transcription, DNA replication, and genome stability. Trends Genet 2023; 39:858-872. [PMID: 37481442 PMCID: PMC10592469 DOI: 10.1016/j.tig.2023.06.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Revised: 06/20/2023] [Accepted: 06/23/2023] [Indexed: 07/24/2023]
Abstract
Transcription elongation requires elaborate coordination between the transcriptional machinery and chromatin regulatory factors to successfully produce RNA while preserving the epigenetic landscape. Recent structural and genomic studies have highlighted that suppressor of Ty 6 (Spt6), a conserved histone chaperone and transcription elongation factor, sits at the crux of the transcription elongation process. Other recent studies have revealed that Spt6 also promotes DNA replication and genome integrity. Here, we review recent studies of Spt6 that have provided new insights into the mechanisms by which Spt6 controls transcription and have revealed the breadth of Spt6 functions in eukaryotic cells.
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Affiliation(s)
- Catherine L W Miller
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA; Laboratory of Genome Maintenance, Rockefeller University, New York, NY 10065, USA
| | - James L Warner
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA
| | - Fred Winston
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA.
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2
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Miller CLW, Winston F. The conserved histone chaperone Spt6 is strongly required for DNA replication and genome stability. Cell Rep 2023; 42:112264. [PMID: 36924499 PMCID: PMC10106089 DOI: 10.1016/j.celrep.2023.112264] [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: 05/06/2022] [Revised: 12/31/2022] [Accepted: 02/27/2023] [Indexed: 03/17/2023] Open
Abstract
Histone chaperones are an important class of proteins that regulate chromatin accessibility for DNA-templated processes. Spt6 is a conserved histone chaperone and key regulator of transcription and chromatin structure. However, its functions outside of these roles have been little explored. In this work, we demonstrate a requirement for S. cerevisiae Spt6 in DNA replication and, more broadly, as a regulator of genome stability. Depletion or mutation of Spt6 impairs DNA replication in vivo. Additionally, spt6 mutants are sensitive to DNA replication stress-inducing agents. Interestingly, this sensitivity is independent of the association of Spt6 with RNA polymerase II (RNAPII), suggesting that spt6 mutants have a transcription-independent impairment of DNA replication. Specifically, genomic studies reveal that spt6 mutants have decreased loading of the MCM replicative helicase at replication origins, suggesting that Spt6 promotes origin licensing. Our results identify Spt6 as a regulator of genome stability, at least in part through a role in DNA replication.
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Affiliation(s)
- Catherine L W Miller
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA; Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA
| | - Fred Winston
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA.
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3
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Owsian D, Gruchota J, Arnaiz O, Nowak JK. The transient Spt4-Spt5 complex as an upstream regulator of non-coding RNAs during development. Nucleic Acids Res 2022; 50:2603-2620. [PMID: 35188560 PMCID: PMC8934623 DOI: 10.1093/nar/gkac106] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Revised: 01/28/2022] [Accepted: 02/04/2022] [Indexed: 12/21/2022] Open
Abstract
The Spt4-Spt5 complex is conserved and essential RNA polymerase elongation factor. To investigate the role of the Spt4-Spt5 complex in non-coding transcription during development, we used the unicellular model Paramecium tetraurelia. In this organism harboring both germline and somatic nuclei, massive transcription of the entire germline genome takes place during meiosis. This phenomenon starts a series of events mediated by different classes of non-coding RNAs that control developmentally programmed DNA elimination. We focused our study on Spt4, a small zinc-finger protein encoded in P. tetraurelia by two genes expressed constitutively and two genes expressed during meiosis. SPT4 genes are not essential in vegetative growth, but they are indispensable for sexual reproduction, even though genes from both expression families show functional redundancy. Silencing of the SPT4 genes resulted in the absence of double-stranded ncRNAs and reduced levels of scnRNAs – 25 nt-long sRNAs produced from these double-stranded precursors in the germline nucleus. Moreover, we observed that the presence of a germline-specific Spt4-Spt5m complex is necessary for transfer of the scnRNA-binding PIWI protein between the germline and somatic nucleus. Our study establishes that Spt4, together with Spt5m, is essential for expression of the germline genome and necessary for developmental genome rearrangements.
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Affiliation(s)
- Dawid Owsian
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5a, 02-106 Warsaw, Poland
| | - Julita Gruchota
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5a, 02-106 Warsaw, Poland
| | - Olivier Arnaiz
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198, Gif-sur-Yvette, France
| | - Jacek K Nowak
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5a, 02-106 Warsaw, Poland
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4
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Cell-cycle phospho-regulation of the kinetochore. Curr Genet 2021; 67:177-193. [PMID: 33221975 DOI: 10.1007/s00294-020-01127-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Revised: 10/27/2020] [Accepted: 10/29/2020] [Indexed: 02/07/2023]
Abstract
The kinetochore is a mega-dalton protein assembly that forms within centromeric regions of chromosomes and directs their segregation during cell division. Here we review cell cycle-mediated phosphorylation events at the kinetochore, with a focus on the budding yeast Saccharomyces cerevisiae and the insight gained from forced associations of kinases and phosphatases. The point centromeres found in the budding yeast S. cerevisiae are one of the simplest such structures found in eukaryotes. The S. cerevisiae kinetochore comprises a single nucleosome, containing a centromere-specific H3 variant Cse4CENP-A, bound to a set of kinetochore proteins that connect to a single microtubule. Despite the simplicity of the budding yeast kinetochore, the proteins are mostly homologous with their mammalian counterparts. In some cases, human proteins can complement their yeast orthologs. Like its mammalian equivalent, the regulation of the budding yeast kinetochore is complex: integrating signals from the cell cycle, checkpoints, error correction, and stress pathways. The regulatory signals from these diverse pathways are integrated at the kinetochore by post-translational modifications, notably phosphorylation and dephosphorylation, to control chromosome segregation. Here we highlight the complex interplay between the activity of the different cell-cycle kinases and phosphatases at the kinetochore, emphasizing how much more we have to understand this essential structure.
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5
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Rayevsky A, Platonov M, Hurmach V, Yakovenko A, Volochnyuk D. Peptidyl inhibition of Spt4-Spt5: Protein-protein inhibitors for targeting the transcriptional pathway related to C9orf72 expansion repeats. J Cell Biochem 2020; 121:4922-4930. [PMID: 32628322 DOI: 10.1002/jcb.29820] [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: 08/21/2019] [Revised: 05/15/2020] [Accepted: 06/12/2020] [Indexed: 11/09/2022]
Abstract
Spt4/Spt5 is an useful target as it is likely a transcription factor that has implications for long non-coding RNA repeats related to frontotemporal dementia (FTD) found in the C9orf72 disease pathology. Inhibitors for Spt4/Spt5 using peptides as a starting point for assays as a means for developing small molecules, which could likely lead to therapeutic development for inhibition for Spt4/Spt5 with CNS characteristics. To elucidate the specific steps of identification and modification of key interacting residues from Spt4/Spt5 complex with further effect prediction, a set of different computational methods was applied. Newly characterized, theoretically derived peptides docked on Spt4/Spt5 models, based on X-ray crystallography sources, allowed us to complete molecular dynamics simulations and docking studies for peptide libraries that give us high confident set of peptides for use to screen for Spt4/Spt5 inhibition. Several peptides with increased specificity to the Spt4/Spt5 interface were found and can be screened in cell-based assays and enzymatic assays for peptide screens that lead to small molecule campaigns. Spt4/Spt5 comprises an attractive target for neurological diseases, and applying these peptides into a screening campaign will promote the goal of therapeutic searches for FTD drug discovery.
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6
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Ólafsson G, Thorpe PH. Polo kinase recruitment via the constitutive centromere-associated network at the kinetochore elevates centromeric RNA. PLoS Genet 2020; 16:e1008990. [PMID: 32810142 PMCID: PMC7455000 DOI: 10.1371/journal.pgen.1008990] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Revised: 08/28/2020] [Accepted: 07/13/2020] [Indexed: 12/23/2022] Open
Abstract
The kinetochore, a multi-protein complex assembled on centromeres, is essential to segregate chromosomes during cell division. Deficiencies in kinetochore function can lead to chromosomal instability and aneuploidy-a hallmark of cancer cells. Kinetochore function is controlled by recruitment of regulatory proteins, many of which have been documented, however their function often remains uncharacterized and many are yet to be identified. To identify candidates of kinetochore regulation we used a proteome-wide protein association strategy in budding yeast and detected many proteins that are involved in post-translational modifications such as kinases, phosphatases and histone modifiers. We focused on the Polo-like kinase, Cdc5, and interrogated which cellular components were sensitive to constitutive Cdc5 localization. The kinetochore is particularly sensitive to constitutive Cdc5 kinase activity. Targeting Cdc5 to different kinetochore subcomplexes produced diverse phenotypes, consistent with multiple distinct functions at the kinetochore. We show that targeting Cdc5 to the inner kinetochore, the constitutive centromere-associated network (CCAN), increases the levels of centromeric RNA via an SPT4 dependent mechanism.
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Affiliation(s)
- Guðjón Ólafsson
- School of Biological and Chemical Sciences, Queen Mary, University of London, London, United Kingdom
| | - Peter H. Thorpe
- School of Biological and Chemical Sciences, Queen Mary, University of London, London, United Kingdom
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7
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Bobkov GOM, Huang A, van den Berg SJW, Mitra S, Anselm E, Lazou V, Schunter S, Feederle R, Imhof A, Lusser A, Jansen LET, Heun P. Spt6 is a maintenance factor for centromeric CENP-A. Nat Commun 2020; 11:2919. [PMID: 32522980 PMCID: PMC7287101 DOI: 10.1038/s41467-020-16695-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2018] [Accepted: 05/19/2020] [Indexed: 12/19/2022] Open
Abstract
Replication and transcription of genomic DNA requires partial disassembly of nucleosomes to allow progression of polymerases. This presents both an opportunity to remodel the underlying chromatin and a danger of losing epigenetic information. Centromeric transcription is required for stable incorporation of the centromere-specific histone dCENP-A in M/G1 phase, which depends on the eviction of previously deposited H3/H3.3-placeholder nucleosomes. Here we demonstrate that the histone chaperone and transcription elongation factor Spt6 spatially and temporarily coincides with centromeric transcription and prevents the loss of old CENP-A nucleosomes in both Drosophila and human cells. Spt6 binds directly to dCENP-A and dCENP-A mutants carrying phosphomimetic residues alleviate this association. Retention of phosphomimetic dCENP-A mutants is reduced relative to wildtype, while non-phosphorylatable dCENP-A retention is increased and accumulates at the centromere. We conclude that Spt6 acts as a conserved CENP-A maintenance factor that ensures long-term stability of epigenetic centromere identity during transcription-mediated chromatin remodeling.
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Affiliation(s)
- Georg O M Bobkov
- Wellcome Centre for Cell Biology, School of Biological Sciences, The University of Edinburgh, Edinburgh, EH9 3BF, UK
- Faculty of Biology, Albert-Ludwigs-Universität Freiburg, 79104, Freiburg, Germany
| | - Anming Huang
- Institute of Molecular Biology, Biocenter, Medical University of Innsbruck, Innrain 80-82, A-6020, Innsbruck, Austria
| | - Sebastiaan J W van den Berg
- Instituto Gulbenkian de Ciência, 2780-156, Oeiras, Portugal
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, UK
| | - Sreyoshi Mitra
- Instituto Gulbenkian de Ciência, 2780-156, Oeiras, Portugal
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, UK
| | - Eduard Anselm
- Wellcome Centre for Cell Biology, School of Biological Sciences, The University of Edinburgh, Edinburgh, EH9 3BF, UK
| | - Vasiliki Lazou
- Wellcome Centre for Cell Biology, School of Biological Sciences, The University of Edinburgh, Edinburgh, EH9 3BF, UK
| | - Sarah Schunter
- Molecular Biology Division, Biomedical Center, Faculty of Medicine, LMU, Munich, Germany
| | - Regina Feederle
- Monoclonal Antibody Core Facility, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), 85764, Neuherberg, Germany
| | - Axel Imhof
- BioMedical Center and Center for Integrated Protein Sciences Munich, Ludwig-Maximilians-University of Munich, Großhaderner Straße 9, 82152, Planegg-Martinsried, Germany
| | - Alexandra Lusser
- Institute of Molecular Biology, Biocenter, Medical University of Innsbruck, Innrain 80-82, A-6020, Innsbruck, Austria
| | - Lars E T Jansen
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, UK
| | - Patrick Heun
- Wellcome Centre for Cell Biology, School of Biological Sciences, The University of Edinburgh, Edinburgh, EH9 3BF, UK.
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8
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Au WC, Zhang T, Mishra PK, Eisenstatt JR, Walker RL, Ocampo J, Dawson A, Warren J, Costanzo M, Baryshnikova A, Flick K, Clark DJ, Meltzer PS, Baker RE, Myers C, Boone C, Kaiser P, Basrai MA. Skp, Cullin, F-box (SCF)-Met30 and SCF-Cdc4-Mediated Proteolysis of CENP-A Prevents Mislocalization of CENP-A for Chromosomal Stability in Budding Yeast. PLoS Genet 2020; 16:e1008597. [PMID: 32032354 PMCID: PMC7032732 DOI: 10.1371/journal.pgen.1008597] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2019] [Revised: 02/20/2020] [Accepted: 01/03/2020] [Indexed: 12/20/2022] Open
Abstract
Restricting the localization of the histone H3 variant CENP-A (Cse4 in yeast, CID in flies) to centromeres is essential for faithful chromosome segregation. Mislocalization of CENP-A leads to chromosomal instability (CIN) in yeast, fly and human cells. Overexpression and mislocalization of CENP-A has been observed in many cancers and this correlates with increased invasiveness and poor prognosis. Yet genes that regulate CENP-A levels and localization under physiological conditions have not been defined. In this study we used a genome-wide genetic screen to identify essential genes required for Cse4 homeostasis to prevent its mislocalization for chromosomal stability. We show that two Skp, Cullin, F-box (SCF) ubiquitin ligases with the evolutionarily conserved F-box proteins Met30 and Cdc4 interact and cooperatively regulate proteolysis of endogenous Cse4 and prevent its mislocalization for faithful chromosome segregation under physiological conditions. The interaction of Met30 with Cdc4 is independent of the D domain, which is essential for their homodimerization and ubiquitination of other substrates. The requirement for both Cdc4 and Met30 for ubiquitination is specifc for Cse4; and a common substrate for Cdc4 and Met30 has not previously been described. Met30 is necessary for the interaction between Cdc4 and Cse4, and defects in this interaction lead to stabilization and mislocalization of Cse4, which in turn contributes to CIN. We provide the first direct link between Cse4 mislocalization to defects in kinetochore structure and show that SCF-mediated proteolysis of Cse4 is a major mechanism that prevents stable maintenance of Cse4 at non-centromeric regions, thus ensuring faithful chromosome segregation. In summary, we have identified essential pathways that regulate cellular levels of endogenous Cse4 and shown that proteolysis of Cse4 by SCF-Met30/Cdc4 prevents mislocalization and CIN in unperturbed cells. Genetic material on each chromosome must be faithfully transmitted to the daughter cell during cell division and chromosomal instability (CIN) results in aneuploidy, a hallmark of cancers. The kinetochore (centromeric DNA and associated proteins) regulates faithful chromosome segregation. Restricting the localization of CENP-A (Cse4 in yeast) to kinetochores is essential for chromosomal stability. Mislocalization of CENP-A contributes to CIN in yeast, fly and human cells and is observed in cancers where it correlates with increased invasiveness and poor prognosis. Hence, identification of pathways that regulate CENP-A levels will help us understand the correlation between CENP-A mislocalization and aneuploidy in cancers. We used a genetic screen to identify essential genes for Cse4 homeostasis and identified a major ubiquitin-dependent pathway where both nuclear F-box proteins, Met30 and Cdc4 of the SCF complex, cooperatively regulate proteolysis of Cse4 to prevent its mislocalization and CIN under physiological conditions. Our studies define a role for SCF-mediated proteolysis of Cse4 as a critical mechanism to ensure faithful chromosome segregation. These studies are significant because mutations in human homologs of Met30 (β-TrCP) and Cdc4 (Fbxw7) have been implicated in cancers, and future studies will determine if SCF-mediated proteolysis of CENP-A prevents its mislocalization for chromosomal stability in human cells.
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Affiliation(s)
- Wei-Chun Au
- Genetics Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, United States of America
| | - Tianyi Zhang
- Genetics Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, United States of America
| | - Prashant K. Mishra
- Genetics Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, United States of America
| | - Jessica R. Eisenstatt
- Genetics Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, United States of America
| | - Robert L. Walker
- Genetics Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, United States of America
| | - Josefina Ocampo
- Division of Developmental Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, United States of America
| | - Anthony Dawson
- Genetics Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, United States of America
| | - Jack Warren
- Genetics Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, United States of America
| | - Michael Costanzo
- Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, ON, Canada
| | | | - Karin Flick
- Department of Biological Chemistry, College of Medicine, University of California, Irvine, CA, United States of America
| | - David J. Clark
- Division of Developmental Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, United States of America
| | - Paul S. Meltzer
- Genetics Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, United States of America
| | - Richard E. Baker
- Department of Microbiology and Physiological Systems, University of Massachusetts Medical School, Worcester, MA, United States of America
| | - Chad Myers
- Department of Computer Science and Engineering, University of Minnesota-Twin Cities, Minneapolis, MN, United States of America
| | - Charles Boone
- Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, ON, Canada
| | - Peter Kaiser
- Department of Biological Chemistry, College of Medicine, University of California, Irvine, CA, United States of America
| | - Munira A. Basrai
- Genetics Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, United States of America
- * E-mail:
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Virulence protein VirD5 of Agrobacterium tumefaciens binds to kinetochores in host cells via an interaction with Spt4. Proc Natl Acad Sci U S A 2017; 114:10238-10243. [PMID: 28874565 DOI: 10.1073/pnas.1706166114] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The bacterium Agrobacterium tumefaciens causes crown gall tumor formation in plants. During infection the bacteria translocate an oncogenic piece of DNA (transferred DNA, T-DNA) into plant cells at the infection site. A number of virulence proteins are cotransported into host cells concomitantly with the T-DNA to effectuate transformation. Using yeast as a model host, we find that one of these proteins, VirD5, localizes to the centromeres/kinetochores in the nucleus of the host cells by its interaction with the conserved protein Spt4. VirD5 promotes chromosomal instability as seen by the high-frequency loss of a minichromosome in yeast. By using both yeast and plant cells with a chromosome that was specifically marked by a lacO repeat, chromosome segregation errors and the appearance of aneuploid cells due to the presence of VirD5 could be visualized in vivo. Thus, VirD5 is a prokaryotic virulence protein that interferes with mitosis.
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10
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Chen R, Zhu J, Dong Y, He C, Hu X. Suppressor of Ty homolog-5, a novel tumor-specific human telomerase reverse transcriptase promoter-binding protein and activator in colon cancer cells. Oncotarget 2016; 6:32841-55. [PMID: 26418880 PMCID: PMC4741733 DOI: 10.18632/oncotarget.5301] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2015] [Accepted: 09/05/2015] [Indexed: 12/14/2022] Open
Abstract
The human telomerase reverse transcriptase (hTERT) promoter promotes differential hTERT gene expression in tumor cells and normal cells. However, information on the mechanisms underlying the differential hTERT transcription and induction of telomerase activity in tumor cells is limited. In the present study, suppressor of Ty homolog-5 (SPT5), a protein encoded by the SUPT5H gene, was identified as a novel tumor-specific hTERT promoter-binding protein and activator in colon cancer cells. We verified the tumor-specific binding activity of SPT5 to the hTERT promoter in vitro and in vivo and detected high expression levels of SUPT5H in colorectal cancer cell lines and primary human colorectal cancer tissues. SUPT5H was more highly expressed in colorectal cancer cases with distant metastasis than in cases without distant metastasis. Inhibition of endogenous SUPT5H expression by SUPT5H gene-specific short hairpin RNAs effectively attenuated hTERT promoter-driven green fluorescent protein (GFP) expression, whereas no detectable effects on CMV promoter-driven GFP expression in the same cells were observed. In addition, inhibition of SUPT5H expression not only effectively repressed telomerase activity, accelerated telomere shortening, and promoted cell senescence in colon cancer cells, but also suppressed cancer cell growth and migration. Our results demonstrated that SPT5 contributes to the up-regulation of hTERT expression and tumor development, and SUPT5H may potentially be used as a novel tumor biomarker and/or cancer therapeutic target.
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Affiliation(s)
- Rui Chen
- Department of Colorectal Surgery, Sir Run Run Shaw Hospital, Zhejiang University, Hangzhou 310016, China
| | - Jing Zhu
- Department of Colorectal Surgery, Sir Run Run Shaw Hospital, Zhejiang University, Hangzhou 310016, China
| | - Yong Dong
- Department of Colorectal Surgery, Sir Run Run Shaw Hospital, Zhejiang University, Hangzhou 310016, China
| | - Chao He
- Department of Colorectal Surgery, Sir Run Run Shaw Hospital, Zhejiang University, Hangzhou 310016, China.,Biomedical Research Center and Key Laboratory of Biotherapy of Zhejiang Province, Sir Run Run Shaw Hospital, Zhejiang University, Hangzhou 310016, China
| | - Xiaotong Hu
- Biomedical Research Center and Key Laboratory of Biotherapy of Zhejiang Province, Sir Run Run Shaw Hospital, Zhejiang University, Hangzhou 310016, China
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11
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Structures and Functions of the Multiple KOW Domains of Transcription Elongation Factor Spt5. Mol Cell Biol 2015. [PMID: 26217010 DOI: 10.1128/mcb.00520-15] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The eukaryotic Spt4-Spt5 heterodimer forms a higher-order complex with RNA polymerase II (and I) to regulate transcription elongation. Extensive genetic and functional data have revealed diverse roles of Spt4-Spt5 in coupling elongation with chromatin modification and RNA-processing pathways. A mechanistic understanding of the diverse functions of Spt4-Spt5 is hampered by challenges in resolving the distribution of functions among its structural domains, including the five KOW domains in Spt5, and a lack of their high-resolution structures. We present high-resolution crystallographic results demonstrating that distinct structures are formed by the first through third KOW domains (KOW1-Linker1 [K1L1] and KOW2-KOW3) of Saccharomyces cerevisiae Spt5. The structure reveals that K1L1 displays a positively charged patch (PCP) on its surface, which binds nucleic acids in vitro, as shown in biochemical assays, and is important for in vivo function, as shown in growth assays. Furthermore, assays in yeast have shown that the PCP has a function that partially overlaps that of Spt4. Synthesis of our results with previous evidence suggests a model in which Spt4 and the K1L1 domain of Spt5 form functionally overlapping interactions with nucleic acids upstream of the transcription bubble, and this mechanism may confer robustness on processes associated with transcription elongation.
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12
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Kang MS, Yu SL, Kim HY, Lim HS, Lee SK. SPT4 increases UV-induced mutagenesis in yeast through impaired nucleotide excision repair. Mol Cell Toxicol 2013. [DOI: 10.1007/s13273-013-0006-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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13
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Hartzog GA, Fu J. The Spt4-Spt5 complex: a multi-faceted regulator of transcription elongation. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2012; 1829:105-15. [PMID: 22982195 DOI: 10.1016/j.bbagrm.2012.08.007] [Citation(s) in RCA: 88] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2012] [Revised: 08/21/2012] [Accepted: 08/29/2012] [Indexed: 10/27/2022]
Abstract
In all domains of life, elongating RNA polymerases require the assistance of accessory factors to maintain their processivity and regulate their rate. Among these elongation factors, the Spt5/NusG factors stand out. Members of this protein family appear to be the only transcription accessory proteins that are universally conserved across all domains of life. In archaea and eukaryotes, Spt5 associates with a second protein, Spt4. In addition to regulating elongation, the eukaryotic Spt4-Spt5 complex appears to couple chromatin modification states and RNA processing to transcription elongation. This review discusses the experimental bases for our current understanding of Spt4-Spt5 function and recent studies that are beginning to elucidate the structure of Spt4-Spt5/RNA polymerase complexes and mechanism of Spt4-Spt5 action. This article is part of a Special Issue entitled: RNA polymerase II Transcript Elongation.
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Affiliation(s)
- Grant A Hartzog
- Department of MCD Biology, University of California, Santa Cruz, CA 95064, USA.
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14
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Stirling PC, Crisp MJ, Basrai MA, Tucker CM, Dunham MJ, Spencer FA, Hieter P. Mutability and mutational spectrum of chromosome transmission fidelity genes. Chromosoma 2011; 121:263-75. [PMID: 22198145 PMCID: PMC3350768 DOI: 10.1007/s00412-011-0356-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2011] [Revised: 12/07/2011] [Accepted: 12/08/2011] [Indexed: 01/10/2023]
Abstract
It has been more than two decades since the original chromosome transmission fidelity (Ctf) screen of Saccharomyces cerevisiae was published. Since that time the spectrum of mutations known to cause Ctf and, more generally, chromosome instability (CIN) has expanded dramatically as a result of systematic screens across yeast mutant arrays. Here we describe a comprehensive summary of the original Ctf genetic screen and the cloning of the remaining complementation groups as efforts to expand our knowledge of the CIN gene repertoire and its mutability in a model eukaryote. At the time of the original screen, it was impossible to predict either the genes and processes that would be overrepresented in a pool of random mutants displaying a Ctf phenotype or what the entire set of genes potentially mutable to Ctf would be. We show that in a collection of 136 randomly selected Ctf mutants, >65% of mutants map to 13 genes, 12 of which are involved in sister chromatid cohesion and/or kinetochore function. Extensive screening of systematic mutant collections has shown that ~350 genes with functions as diverse as RNA processing and proteasomal activity mutate to cause a Ctf phenotype and at least 692 genes are required for faithful chromosome segregation. The enrichment of random Ctf alleles in only 13 of ~350 possible Ctf genes suggests that these genes are more easily mutable to cause genome instability than the others. These observations inform our understanding of recurring CIN mutations in human cancers where presumably random mutations are responsible for initiating the frequently observed CIN phenotype of tumors.
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Affiliation(s)
- Peter C Stirling
- Michael Smith Laboratories, University of British Columbia, Vancouver, BC, Canada, V6T1Z4
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15
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Latham JA, Chosed RJ, Wang S, Dent SYR. Chromatin signaling to kinetochores: transregulation of Dam1 methylation by histone H2B ubiquitination. Cell 2011; 146:709-19. [PMID: 21884933 DOI: 10.1016/j.cell.2011.07.025] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2010] [Revised: 06/15/2011] [Accepted: 07/19/2011] [Indexed: 11/25/2022]
Abstract
Histone H3K4 trimethylation by the Set1/MLL family of proteins provides a hallmark for transcriptional activity from yeast to humans. In S. cerevisiae, H3K4 methylation is mediated by the Set1-containing COMPASS complex and is regulated in trans by prior ubiquitination of histone H2BK123. All of the events that regulate H2BK123ub and H3K4me are thought to occur at gene promoters. Here we report that this pathway is indispensable for methylation of the only other known substrate of Set1, K233 in Dam1, at kinetochores. Deletion of RAD6, BRE1, or Paf1 complex members abolishes Dam1 methylation, as does mutation of H2BK123. Our results demonstrate that Set1-mediated methylation is regulated by a general pathway regardless of substrate that is composed of transcriptional regulatory factors functioning independently of transcription. Moreover, our data identify a node of regulatory crosstalk in trans between a histone modification and modification on a nonhistone protein, demonstrating that changing chromatin states can signal functional changes in other essential cellular proteins and machineries.
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Affiliation(s)
- John A Latham
- Program in Genes and Development, University of Texas M.D. Anderson Cancer Center, Smithville, TX 78957, USA
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16
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The Paf1 complex represses SER3 transcription in Saccharomyces cerevisiae by facilitating intergenic transcription-dependent nucleosome occupancy of the SER3 promoter. EUKARYOTIC CELL 2011; 10:1283-94. [PMID: 21873510 DOI: 10.1128/ec.05141-11] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Previous studies have shown that repression of the Saccharomyces cerevisiae SER3 gene is dependent on transcription of SRG1 from noncoding DNA initiating within the intergenic region 5' of SER3 and extending across the SER3 promoter region. By a mechanism dependent on the activities of the Swi/Snf chromatin remodeling factor, the HMG-like factor Spt2, and the Spt6 and Spt16 histone chaperones, SRG1 transcription deposits nucleosomes over the SER3 promoter to prevent transcription factors from binding and activating SER3. In this study, we uncover a role for the Paf1 transcription elongation complex in SER3 repression. We find that SER3 repression is primarily dependent on the Paf1 and Ctr9 subunits of this complex, with minor contributions by the Rtf1, Cdc73, and Leo1 subunits. We show that the Paf1 complex localizes to the SRG1 transcribed region under conditions that repress SER3, consistent with it having a direct role in mediating SRG1 transcription-dependent SER3 repression. Importantly, we show that the defect in SER3 repression in strains lacking Paf1 subunits is not a result of reduced SRG1 transcription or reduced levels of known Paf1 complex-dependent histone modifications. Rather, we find that strains lacking subunits of the Paf1 complex exhibit reduced nucleosome occupancy and reduced recruitment of Spt16 and, to a lesser extent, Spt6 at the SER3 promoter. Taken together, our results suggest that Paf1 and Ctr9 repress SER3 by maintaining SRG1 transcription-dependent nucleosome occupancy.
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17
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Spt6 is required for heterochromatic silencing in the fission yeast Schizosaccharomyces pombe. Mol Cell Biol 2011; 31:4193-204. [PMID: 21844224 DOI: 10.1128/mcb.05568-11] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Spt6 is a conserved factor, critically required for several transcription- and chromatin-related processes. We now show that Spt6 and its binding partner, Iws1, are required for heterochromatic silencing in Schizosaccharomyces pombe. Our studies demonstrate that Spt6 is required for silencing of all heterochromatic loci and that an spt6 mutant has an unusual combination of heterochromatic phenotypes compared to previously studied silencing mutants. Unexpectedly, we find normal nucleosome positioning over heterochromatin and normal levels of histone H3K9 dimethylation at the endogenous pericentric repeats. However, we also find greatly reduced levels of H3K9 trimethylation, elevated levels of H3K14 acetylation, reduced recruitment of several silencing factors, and defects in heterochromatin spreading. Our evidence suggests that Spt6 plays a role at both the transcriptional and posttranscriptional levels; in an spt6 mutant, RNA polymerase II (RNAPII) occupancy at the pericentric regions is only modestly increased, while production of small interfering RNAs (siRNAs) is lost. Taken together, our results suggest that Spt6 is required for multiple steps in heterochromatic silencing by controlling chromatin, transcriptional, and posttranscriptional processes.
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18
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Hirtreiter A, Damsma GE, Cheung ACM, Klose D, Grohmann D, Vojnic E, Martin ACR, Cramer P, Werner F. Spt4/5 stimulates transcription elongation through the RNA polymerase clamp coiled-coil motif. Nucleic Acids Res 2010; 38:4040-51. [PMID: 20197319 PMCID: PMC2896526 DOI: 10.1093/nar/gkq135] [Citation(s) in RCA: 138] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Spt5 is the only known RNA polymerase-associated factor that is conserved in all three domains of life. We have solved the structure of the Methanococcus jannaschii Spt4/5 complex by X-ray crystallography, and characterized its function and interaction with the archaeal RNAP in a wholly recombinant in vitro transcription system. Archaeal Spt4 and Spt5 form a stable complex that associates with RNAP independently of the DNA–RNA scaffold of the elongation complex. The association of Spt4/5 with RNAP results in a stimulation of transcription processivity, both in the absence and the presence of the non-template strand. A domain deletion analysis reveals the molecular anatomy of Spt4/5—the Spt5 Nus-G N-terminal (NGN) domain is the effector domain of the complex that both mediates the interaction with RNAP and is essential for its elongation activity. Using a mutagenesis approach, we have identified a hydrophobic pocket on the Spt5 NGN domain as binding site for RNAP, and reciprocally the RNAP clamp coiled-coil motif as binding site for Spt4/5.
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Affiliation(s)
- Angela Hirtreiter
- Division of Biosciences, University College London, Institute for Structural and Molecular Biology, Darwin Building, Gower Street, London WC1E 6BT, UK
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19
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Schwer B, Schneider S, Pei Y, Aronova A, Shuman S. Characterization of the Schizosaccharomyces pombe Spt5-Spt4 complex. RNA (NEW YORK, N.Y.) 2009; 15:1241-50. [PMID: 19460865 PMCID: PMC2704081 DOI: 10.1261/rna.1572709] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
The Spt5-Spt4 complex regulates early transcription elongation by RNA polymerase II and has an imputed role in pre-mRNA processing via its physical association with mRNA capping enzymes. Here we characterize the Schizosaccharomyces pombe core Spt5-Spt4 complex as a heterodimer and map a trypsin-resistant Spt4-binding domain within the Spt5 subunit. A genetic analysis of Spt4 in S. pombe revealed it to be inessential for growth at 25 degrees C-30 degrees C but critical at 37 degrees C. These results echo the conditional spt4Delta growth phenotype in budding yeast, where we find that Saccharomyces cerevisiae and S. pombe Spt4 are functionally interchangeable. Complementation of S. cerevisiae spt4Delta and a two-hybrid assay for Spt4-Spt5 interaction provided a readout of the effects of 33 missense and truncation mutations on S. pombe Spt4 function in vivo, which were interpreted in light of the recent crystal structure of S. cerevisiae Spt4 fused to a fragment of Spt5. Our results highlight the importance of the Spt4 Zn2+-binding residues--Cys12, Cys15, Cys29, and Asp32--and of Ser57, a conserved constituent of the Spt4-Spt5 interface. The 990-amino acid S. pombe Spt5 protein has an exceptionally regular carboxyl-terminal domain (CTD) composed of 18 nonapeptide repeats. We find that as few as three nonamer repeats sufficed for S. pombe growth, but only when Spt4 was present. Synthetic lethality of the spt5(1-835) spt4Delta double mutant at 34 degrees C suggests that interaction of Spt4 with the central domain of Spt5 overlaps functionally with the Spt5 CTD.
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Affiliation(s)
- Beate Schwer
- Department of Microbiology and Immunology, Weill Cornell Medical College, New York, New York 10065, USA.
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20
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Komori T, Inukai N, Yamada T, Yamaguchi Y, Handa H. Role of human transcription elongation factor DSIF in the suppression of senescence and apoptosis. Genes Cells 2009; 14:343-54. [PMID: 19210550 DOI: 10.1111/j.1365-2443.2008.01273.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
DSIF is an evolutionarily conserved, ubiquitously expressed, heterodimeric transcription elongation factor composed of two subunits, Spt4 and Spt5. Previous biochemical studies have shown that DSIF positively and negatively regulates RNA polymerase II elongation in collaboration with other protein factors. While several data suggest that DSIF is a 'general' elongation factor, there is also evidence that DSIF exerts a tissue- and gene-specific function. Here we sought to address the question of whether physiological functions of DSIF are general or specific, by using a sophisticated knockdown approach and gene expression microarray analysis. We found that Spt5 is essential for cell growth of various human cell lines and that Spt5 knockdown causes senescence and apoptosis. However, Spt5 knockdown affects a surprisingly small number of genes. In Spt5 knockdown cells, the p53 signaling pathway is activated and mediates part of the knockdown-induced transcriptional change, but apoptotic cell death occurs in the absence of p53. Structure-function analysis of Spt5 shows that the C-terminal approximately 300 amino acid residues are not required to support cell proliferation. These results suggest that one of the functions of Spt5 is to suppress senescence and apoptosis, and that this function is exerted through its association with Spt4 and Pol II.
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Affiliation(s)
- Toshiharu Komori
- Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, 4259 Nagatsuta, Yokohama 226-8501, Japan
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21
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Guo M, Xu F, Yamada J, Egelhofer T, Gao Y, Hartzog GA, Teng M, Niu L. Core structure of the yeast spt4-spt5 complex: a conserved module for regulation of transcription elongation. Structure 2009; 16:1649-58. [PMID: 19000817 DOI: 10.1016/j.str.2008.08.013] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2008] [Revised: 08/20/2008] [Accepted: 08/20/2008] [Indexed: 11/30/2022]
Abstract
The Spt4-Spt5 complex is an essential RNA polymerase II elongation factor found in all eukaryotes and important for gene regulation. We report here the crystal structure of Saccharomyces cerevisiae Spt4 bound to the NGN domain of Spt5. This structure reveals that Spt4-Spt5 binding is governed by an acid-dipole interaction between Spt5 and Spt4. Mutations that disrupt this interaction disrupt the complex. Residues forming this pivotal interaction are conserved in the archaeal homologs of Spt4 and Spt5, which we show also form a complex. Even though bacteria lack a Spt4 homolog, the NGN domains of Spt5 and its bacterial homologs are structurally similar. Spt4 is located at a position that may help to maintain the functional conformation of the following KOW domains in Spt5. This structural and evolutionary perspective of the Spt4-Spt5 complex and its homologs suggest that it is an ancient, core component of the transcription elongation machinery.
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Affiliation(s)
- Min Guo
- Hefei National Laboratory for Physical Sciences at Microscale and Key Laboratory of Structural Biology, School of Life Sciences, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230027, China
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22
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Altered dosage and mislocalization of histone H3 and Cse4p lead to chromosome loss in Saccharomyces cerevisiae. Genetics 2008; 179:263-75. [PMID: 18458100 DOI: 10.1534/genetics.108.088518] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Cse4p is an essential histone H3 variant in Saccharomyces cerevisiae that defines centromere identity and is required for proper segregation of chromosomes. In this study, we investigated phenotypic consequences of Cse4p mislocalization and increased dosage of histone H3 and Cse4p, and established a direct link between histone stoichiometry, mislocalization of Cse4p, and chromosome segregation. Overexpression of the stable Cse4p mutant, cse4(K16R), resulted in its mislocalization, increased association with chromatin, and a high rate of chromosome loss, all of which were suppressed by constitutive expression of histone H3 (delta 16H3). We determined that delta 16H3 did not lead to increased chromosome loss; however, increasing the dosage of histone H3 (GALH3) resulted in significant chromosome loss due to reduced levels of centromere (CEN)-associated Cse4p and synthetic dosage lethality (SDL) in kinetochore mutants. These phenotypes were suppressed by GALCSE4. We conclude that the chromosome missegregation of GALcse4(K16R) and GALH3 strains is due to mislocalization and a functionally compromised kinetochore, respectively. Suppression of these phenotypes by histone delta 16H3 and GALCSE4 supports the conclusion that proper stoichiometry affects the localization of histone H3 and Cse4p and is thus essential for accurate chromosome segregation.
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23
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Bennett CB, Westmoreland TJ, Verrier CS, Blanchette CAB, Sabin TL, Phatnani HP, Mishina YV, Huper G, Selim AL, Madison ER, Bailey DD, Falae AI, Galli A, Olson JA, Greenleaf AL, Marks JR. Yeast screens identify the RNA polymerase II CTD and SPT5 as relevant targets of BRCA1 interaction. PLoS One 2008; 3:e1448. [PMID: 18197258 PMCID: PMC2174531 DOI: 10.1371/journal.pone.0001448] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2007] [Accepted: 12/13/2007] [Indexed: 11/30/2022] Open
Abstract
BRCA1 has been implicated in numerous DNA repair pathways that maintain genome integrity, however the function responsible for its tumor suppressor activity in breast cancer remains obscure. To identify the most highly conserved of the many BRCA1 functions, we screened the evolutionarily distant eukaryote Saccharomyces cerevisiae for mutants that suppressed the G1 checkpoint arrest and lethality induced following heterologous BRCA1 expression. A genome-wide screen in the diploid deletion collection combined with a screen of ionizing radiation sensitive gene deletions identified mutants that permit growth in the presence of BRCA1. These genes delineate a metabolic mRNA pathway that temporally links transcription elongation (SPT4, SPT5, CTK1, DEF1) to nucleopore-mediated mRNA export (ASM4, MLP1, MLP2, NUP2, NUP53, NUP120, NUP133, NUP170, NUP188, POM34) and cytoplasmic mRNA decay at P-bodies (CCR4, DHH1). Strikingly, BRCA1 interacted with the phosphorylated RNA polymerase II (RNAPII) carboxy terminal domain (P-CTD), phosphorylated in the pattern specified by the CTDK-I kinase, to induce DEF1-dependent cleavage and accumulation of a RNAPII fragment containing the P-CTD. Significantly, breast cancer associated BRCT domain defects in BRCA1 that suppressed P-CTD cleavage and lethality in yeast also suppressed the physical interaction of BRCA1 with human SPT5 in breast epithelial cells, thus confirming SPT5 as a relevant target of BRCA1 interaction. Furthermore, enhanced P-CTD cleavage was observed in both yeast and human breast cells following UV-irradiation indicating a conserved eukaryotic damage response. Moreover, P-CTD cleavage in breast epithelial cells was BRCA1-dependent since damage-induced P-CTD cleavage was only observed in the mutant BRCA1 cell line HCC1937 following ectopic expression of wild type BRCA1. Finally, BRCA1, SPT5 and hyperphosphorylated RPB1 form a complex that was rapidly degraded following MMS treatment in wild type but not BRCA1 mutant breast cells. These results extend the mechanistic links between BRCA1 and transcriptional consequences in response to DNA damage and suggest an important role for RNAPII P-CTD cleavage in BRCA1-mediated cancer suppression.
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Affiliation(s)
- Craig B Bennett
- Department of Surgery, Duke University Medical Center, Durham, North Carolina, United States of America.
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24
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Duina AA, Rufiange A, Bracey J, Hall J, Nourani A, Winston F. Evidence that the localization of the elongation factor Spt16 across transcribed genes is dependent upon histone H3 integrity in Saccharomyces cerevisiae. Genetics 2007; 177:101-12. [PMID: 17603125 PMCID: PMC2013732 DOI: 10.1534/genetics.106.067140] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A previous study of histone H3 in Saccharomyces cerevisiae identified a mutant with a single amino acid change, leucine 61 to tryptophan, that confers several transcriptional defects. We now present several lines of evidence that this H3 mutant, H3-L61W, is impaired at the level of transcription elongation, likely by altered interactions with the conserved factor Spt16, a subunit of the transcription elongation complex yFACT. First, a selection for suppressors of the H3-L61W cold-sensitive phenotype has identified novel mutations in the gene encoding Spt16. These genetic interactions are allele specific, suggesting a direct interaction between H3 and Spt16. Second, similar to several other elongation and chromatin mutants, including spt16 mutants, an H3-L61W mutant allows transcription from a cryptic promoter within the FLO8 coding region. Finally, chromatin-immunoprecipitation experiments show that in an H3-L61W mutant there is a dramatically altered profile of Spt16 association over transcribed regions, with reduced levels over 5'-coding regions and elevated levels over the 3' regions. Taken together, these and other results provide strong evidence that the integrity of histone H3 is crucial for ensuring proper distribution of Spt16 across transcribed genes and suggest a model for the mechanism by which Spt16 normally dissociates from DNA following transcription.
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Affiliation(s)
- Andrea A Duina
- Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA
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25
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Klose RJ, Gardner KE, Liang G, Erdjument-Bromage H, Tempst P, Zhang Y. Demethylation of histone H3K36 and H3K9 by Rph1: a vestige of an H3K9 methylation system in Saccharomyces cerevisiae? Mol Cell Biol 2007; 27:3951-61. [PMID: 17371840 PMCID: PMC1900024 DOI: 10.1128/mcb.02180-06] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2006] [Revised: 01/08/2007] [Accepted: 03/12/2007] [Indexed: 11/20/2022] Open
Abstract
Histone methylation is an important posttranslational modification that contributes to chromatin-based processes including transcriptional regulation, DNA repair, and epigenetic inheritance. In the budding yeast Saccharomyces cerevisiae, histone lysine methylation occurs on histone H3 lysines 4, 36, and 79, and its deposition is coupled mainly to transcription. Until recently, histone methylation was considered to be irreversible, but the identification of histone demethylase enzymes has revealed that this modification can be dynamically regulated. In budding yeast, there are five proteins that contain the JmjC domain, a signature motif found in a large family of histone demethylases spanning many organisms. One JmjC-domain-containing protein in budding yeast, Jhd1, has recently been identified as being a histone demethylase that targets H3K36 modified in the di- and monomethyl state. Here, we identify a second JmjC-domain-containing histone demethylase, Rph1, which can specifically demethylate H3K36 tri- and dimethyl modification states. Surprisingly, Rph1 can remove H3K9 methylation, a histone modification not found in budding yeast chromatin. The capacity of Rph1 to demethylate H3K9 provides the first indication that S. cerevisiae may have once encoded an H3K9 methylation system and suggests that Rph1 is a functional vestige of this modification system.
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Affiliation(s)
- Robert J Klose
- Department of Biochemistry and Biophysics, Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7295, USA
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26
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Fang J, Hogan GJ, Liang G, Lieb JD, Zhang Y. The Saccharomyces cerevisiae histone demethylase Jhd1 fine-tunes the distribution of H3K36me2. Mol Cell Biol 2007; 27:5055-65. [PMID: 17470555 PMCID: PMC1951470 DOI: 10.1128/mcb.00127-07] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Histone methylation plays important roles in the regulation of chromatin dynamics and transcription. Steady-state levels of histone lysine methylation are regulated by a balance between enzymes that catalyze either the addition or removal of methyl groups. Using an activity-based biochemical approach, we recently uncovered the JmjC domain as an evolutionarily conserved signature motif for histone demethylases. Furthermore, we demonstrated that Jhd1, a JmjC domain-containing protein in Saccharomyces cerevisiae, is an H3K36-specific demethylase. Here we report further characterization of Jhd1. Similar to its mammalian homolog, Jhd1-catalyzed histone demethylation requires iron and alpha-ketoglutarate as cofactors. Mutation and deletion studies indicate that the JmjC domain and adjacent sequences are critical for Jhd1 enzymatic activity, while the N-terminal PHD domain is dispensable. Overexpression of JHD1 results in a global reduction of H3K36 methylation in vivo. Finally, chromatin immunoprecipitation-coupled microarray studies reveal subtle changes in the distribution of H3K36me2 upon overexpression or deletion of JHD1. Our studies establish Jhd1 as a histone demethylase in budding yeast and suggest that Jhd1 functions to maintain the fidelity of histone methylation patterns along transcription units.
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Affiliation(s)
- Jia Fang
- Howard Hughes Medical Institute, University of North Carolina at Chapel Hill, NC 27599, USA
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27
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Kastenmayer JP, Ni L, Chu A, Kitchen LE, Au WC, Yang H, Carter CD, Wheeler D, Davis RW, Boeke JD, Snyder MA, Basrai MA. Functional genomics of genes with small open reading frames (sORFs) in S. cerevisiae. Genome Res 2006; 16:365-73. [PMID: 16510898 PMCID: PMC1415214 DOI: 10.1101/gr.4355406] [Citation(s) in RCA: 157] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Genes with small open reading frames (sORFs; <100 amino acids) represent an untapped source of important biology. sORFs largely escaped analysis because they were difficult to predict computationally and less likely to be targeted by genetic screens. Thus, the substantial number of sORFs and their potential importance have only recently become clear. To investigate sORF function, we undertook the first functional studies of sORFs in any system, using the model eukaryote Saccharomyces cerevisiae. Based on independent experimental approaches and computational analyses, evidence exists for 299 sORFs in the S. cerevisiae genome, representing approximately 5% of the annotated ORFs. We determined that a similar percentage of sORFs are annotated in other eukaryotes, including humans, and 184 of the S. cerevisiae sORFs exhibit similarity with ORFs in other organisms. To investigate sORF function, we constructed a collection of gene-deletion mutants of 140 newly identified sORFs, each of which contains a strain-specific "molecular barcode," bringing the total number of sORF deletion strains to 247. Phenotypic analyses of the new gene-deletion strains identified 22 sORFs required for haploid growth, growth at high temperature, growth in the presence of a nonfermentable carbon source, or growth in the presence of DNA damage and replication-arrest agents. We provide a collection of sORF deletion strains that can be integrated into the existing deletion collection as a resource for the yeast community for elucidating gene function. Moreover, our analyses of the S. cerevisiae sORFs establish that sORFs are conserved across eukaryotes and have important biological functions.
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Affiliation(s)
- James P Kastenmayer
- Genetics Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20889, USA
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28
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Schneider DA, French SL, Osheim YN, Bailey AO, Vu L, Dodd J, Yates JR, Beyer AL, Nomura M. RNA polymerase II elongation factors Spt4p and Spt5p play roles in transcription elongation by RNA polymerase I and rRNA processing. Proc Natl Acad Sci U S A 2006; 103:12707-12. [PMID: 16908835 PMCID: PMC1568913 DOI: 10.1073/pnas.0605686103] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Previous investigations into the mechanisms that control RNA Polymerase (Pol) I transcription have primarily focused on the process of transcription initiation, thus little is known regarding postinitiation steps in the transcription cycle. Spt4p and Spt5p are conserved throughout eukaryotes, and they affect elongation by Pol II. We have found that these two proteins copurify with Pol I and associate with the rDNA in vivo. Disruption of the gene for Spt4p resulted in a modest decrease in growth and rRNA synthesis rates at the permissive temperature, 30 degrees C. Furthermore, biochemical and EM analyses showed clear defects in rRNA processing. These data suggest that Spt4p, Spt5p, and, potentially, other regulators of Pol I transcription elongation play important roles in coupling rRNA transcription to its processing and ribosome assembly.
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Affiliation(s)
- D. A. Schneider
- *Department of Biological Chemistry, University of California, Irvine, CA 92697-1700
| | - S. L. French
- Department of Microbiology, University of Virginia Health System, Charlottesville, VA 22908-0734; and
| | - Y. N. Osheim
- Department of Microbiology, University of Virginia Health System, Charlottesville, VA 22908-0734; and
| | - A. O. Bailey
- Department of Cell Biology, The Scripps Research Institute, La Jolla, CA 92130
| | - L. Vu
- *Department of Biological Chemistry, University of California, Irvine, CA 92697-1700
| | - J. Dodd
- *Department of Biological Chemistry, University of California, Irvine, CA 92697-1700
| | - J. R. Yates
- Department of Cell Biology, The Scripps Research Institute, La Jolla, CA 92130
| | - A. L. Beyer
- Department of Microbiology, University of Virginia Health System, Charlottesville, VA 22908-0734; and
- To whom correspondence may be addressed. E-mail:
or
| | - M. Nomura
- *Department of Biological Chemistry, University of California, Irvine, CA 92697-1700
- To whom correspondence may be addressed. E-mail:
or
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29
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Carter CD, Kitchen LE, Au WC, Babic CM, Basrai MA. Loss of SOD1 and LYS7 sensitizes Saccharomyces cerevisiae to hydroxyurea and DNA damage agents and downregulates MEC1 pathway effectors. Mol Cell Biol 2005; 25:10273-85. [PMID: 16287844 PMCID: PMC1291217 DOI: 10.1128/mcb.25.23.10273-10285.2005] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Aerobic metabolism produces reactive oxygen species, including superoxide anions, which cause DNA damage unless removed by scavengers such as superoxide dismutases. We show that loss of the Cu,Zn-dependent superoxide dismutase, SOD1, or its copper chaperone, LYS7, confers oxygen-dependent sensitivity to replication arrest and DNA damage in Saccharomyces cerevisiae. We also find that sod1Delta strains, and to a lesser extent lys7Delta strains, when arrested with hydroxyurea (HU) show reduced induction of the MEC1 pathway effector Rnr3p and of Hug1p. The HU sensitivity of sod1Delta and lys7Delta strains is suppressed by overexpression of TKL1, a transketolase that generates NADPH, which balances redox in the cell and is required for ribonucleotide reductase activity. Our results suggest that the MEC1 pathway in sod1Delta mutant strains is sensitive to the altered cellular redox state due to increased superoxide anions and establish a new relationship between SOD1, LYS7, and the MEC1-mediated checkpoint response to replication arrest and DNA damage in S. cerevisiae.
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Affiliation(s)
- Carole D Carter
- Genetics Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, National Naval Medical Center, Building 8, Room 5101, 8901 Wisconsin Ave., Bethesda, MD 20889-5105, USA
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Gillis AN, Thomas S, Hansen SD, Kaplan KB. A novel role for the CBF3 kinetochore-scaffold complex in regulating septin dynamics and cytokinesis. J Cell Biol 2005; 171:773-84. [PMID: 16330709 PMCID: PMC2171293 DOI: 10.1083/jcb.200507017] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2005] [Accepted: 10/24/2005] [Indexed: 11/29/2022] Open
Abstract
In budding yeast, the kinetochore scaffold complex centromere binding factor 3 (CBF3) is required to form kinetochores on centromere DNA and to allow proper chromosome segregation. We have previously shown that SKP1 and SGT1 balance the assembly and turnover of CBF3 complexes, a cycle that we suggest is independent of its role in chromosome segregation (Rodrigo-Brenni, M.C., S. Thomas, D.C. Bouck, and K.B. Kaplan. 2004. Mol. Biol. Cell. 15:3366-3378). We provide evidence that this cycle contributes to a second, kinetochore-independent function of CBF3. In this study, we show that inhibiting the assembly of CBF3 causes disorganized septins and defects in cell polarity that give rise to cytokinesis failures. Specifically, we show that septin ring separation and disassembly is delayed in anaphase, suggesting that CBF3 regulates septin dynamics. Only mutations that affect the CBF3 cycle, and not mutants in outer kinetochore subunits, cause defects in septins. These results demonstrate a novel role for CBF3 in regulating cytokinesis, a role that is reminiscent of passenger proteins. Consistent with this possibility, we find that CBF3 interacts with Bir1p, the homologue of the passenger protein Survivin. Mutants in Bir1p similarly affect septin organization, leading us to propose that CBF3 and Bir1p act as passenger proteins to coordinate chromosome segregation with cytokinesis.
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Affiliation(s)
- Amethyst N Gillis
- The Section of Molecular and Cellular Biology, University of California, Davis, Davis, CA 95616, USA
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31
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Hentges KE, Kyttälä M, Justice MJ, Peltonen L. Comparative physical maps of the human and mouse Meckel syndrome critical regions. Mamm Genome 2004; 15:252-64. [PMID: 15112103 DOI: 10.1007/s00335-003-2303-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2003] [Accepted: 11/25/2003] [Indexed: 10/26/2022]
Abstract
Meckel syndrome (MKS-OMIM 24900) is an autosomal recessive disease characterized by cystic kidneys, occipital encephalocele, polydactyly, and fibrotic changes of the liver, typically resulting in postnatal death. A Meckel syndrome critical region (MKS1) maps to human Chromosome (Chr) 17, in a region of homology to mouse Chr 11. Here we report the comparison of human Chr 17q23 with mouse Chr 11. We have generated physical maps of the human and mouse MKS1 critical regions. Additionally, we have created a transcript map of the MKS1 critical region in both species. By comparing these physical maps, we observe a high degree of similarity in gene order in the human and mouse Meckel syndrome critical regions. We have also examined the expression patterns of genes in the MKS1 region to assess their potential as MKS1 candidates. Finally, we have analyzed genes present in the other Meckel syndrome critical regions, MKS2 and MKS3, to determine whether any of the candidate genes for the three MKS loci have similar gene functions or are members of a common biological pathway.
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Affiliation(s)
- Kathryn E Hentges
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030, USA
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32
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Crotti LB, Basrai MA. Functional roles for evolutionarily conserved Spt4p at centromeres and heterochromatin in Saccharomyces cerevisiae. EMBO J 2004; 23:1804-14. [PMID: 15057281 PMCID: PMC394231 DOI: 10.1038/sj.emboj.7600161] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2003] [Accepted: 02/16/2004] [Indexed: 11/09/2022] Open
Abstract
The kinetochore (centromeric DNA and associated proteins) mediates the attachment of chromosomes to the mitotic spindle apparatus and is required for faithful chromosome transmission. We established that evolutionarily conserved Saccharomyces cerevisiae SPT4, previously identified in genetic screens for defects in chromosome transmission fidelity (ctf), encodes a new structural component of specialized chromatin at kinetochores and heterochromatic loci, with roles in kinetochore function and gene silencing. Using chromatin immunoprecipitation assays (ChIP), we determined that kinetochore proteins Ndc10p, Cac1p, and Hir1p are required for the association of Spt4p to centromeric (CEN) loci. Absence of functional Spt4p leads to altered chromatin structure at the CEN DNA and mislocalization of the mammalian CENP-A homolog Cse4p to noncentromeric loci. Spt4p associates with telomeres (TEL) and HMRa loci in a Sir3p-dependent manner and is required for transcriptional gene silencing. We show that a human homolog of SPT4 (HsSPT4) complements Scspt4-silencing defects and associates with ScCEN DNA in an Ndc10p-dependent manner. Our results highlight the evolutionary conservation of pathways required for genome stability in yeast and humans.
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Affiliation(s)
| | - Munira A Basrai
- Genetics Branch, National Cancer Institute, Bethesda, MD, USA
- Genetics Branch, National Cancer Institute, NNMC Bldg. 8, Room 5101, 8901 Wisconsin Avenue, Bethesda, MD 20889-5105, USA. Tel.: +1 301 402 2552; Fax: +1 301 480 0380; E-mail:
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Makhnevych T, Lusk CP, Anderson AM, Aitchison JD, Wozniak RW. Cell cycle regulated transport controlled by alterations in the nuclear pore complex. Cell 2004; 115:813-23. [PMID: 14697200 DOI: 10.1016/s0092-8674(03)00986-3] [Citation(s) in RCA: 128] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Eukaryotic cells have developed mechanisms for regulating the nuclear transport of macromolecules that control various cellular events including movement through defined stages of the cell cycle. In yeast cells, where the nuclear envelope remains intact throughout the cell cycle, these transport regulatory mechanisms must also function during mitosis. We have uncovered a mechanism for regulating transport that is controlled by M phase specific molecular rearrangements in the nuclear pore complex (NPC). These changes allow a transport inhibitory nucleoporin, Nup53p, to bind the karyopherin Kap121p specifically during mitosis, slowing its movement through the NPC and inducing cargo release. Yeast strains that possess defects in the function of Kap121p or the fidelity of the inhibitory pathway are delayed in mitosis. We propose that fluctuations in Kap121p transport mediated by the NPC contribute to controlling the subcellular distribution of molecules that direct progression through mitosis.
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Affiliation(s)
- Taras Makhnevych
- Department of Cell Biology, University of Alberta, Edmonton, Alberta, Canada T6G 2H7
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Kim DK, Inukai N, Yamada T, Furuya A, Sato H, Yamaguchi Y, Wada T, Handa H. Structure-function analysis of human Spt4: evidence that hSpt4 and hSpt5 exert their roles in transcriptional elongation as parts of the DSIF complex. Genes Cells 2003; 8:371-8. [PMID: 12653964 DOI: 10.1046/j.1365-2443.2003.00638.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND The human Spt4/Spt5 complex, termed DRB-sensitivity inducing factor (DSIF) is a dual regulator of transcription that stimulates, or, when cooperating with negative elongation factor (NELF), represses RNA polymerase II (RNAPII) elongation. Spt4 and Spt5 are also thought to be involved in mRNA capping, homologous DNA recombination, and transcription-coupled DNA repair. As a first step to understanding how these proteins regulate diverse cellular processes, we investigated the structure and function of hSpt4 in vitro. RESULTS Immunodepletion of hSpt5 from HeLa nuclear extracts resulted in the efficient co-depletion of hSpt4. Using DSIF-depleted nuclear extracts and a series of Spt4 mutants, we examined the amino acid sequence of hSpt4 which was important for hSpt5 binding and for transcriptional repression and activation by DSIF. Unexpectedly, the zinc finger of hSpt4, which is critical for the yeast counterpart to function in vivo, was dispensable for hSpt5 binding and for transcriptional regulation in vitro. CONCLUSION These and other results suggest: (i) that the central region of hSpt4 is necessary and sufficient for its function in vitro and (ii) that there is no free hSpt4 or hSpt5 in cells. We propose that hSpt4 and hSpt5 exert their roles in transcriptional regulation, and possibly in other nuclear processes, as parts of the DSIF complex.
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Affiliation(s)
- Dong-Ki Kim
- Graduate School of Bioscience and Biotechnology, and Frontier Collaborative Research Center, Tokyo Institute of Technology, Yokohama 226-8501, Japan
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Iouk T, Kerscher O, Scott RJ, Basrai MA, Wozniak RW. The yeast nuclear pore complex functionally interacts with components of the spindle assembly checkpoint. J Cell Biol 2002; 159:807-19. [PMID: 12473689 PMCID: PMC2173375 DOI: 10.1083/jcb.200205068] [Citation(s) in RCA: 135] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Aphysical and functional link between the nuclear pore complex (NPC) and the spindle checkpoint machinery has been established in the yeast Saccharomyces cerevisiae. We show that two proteins required for the execution of the spindle checkpoint, Mad1p and Mad2p, reside predominantly at the NPC throughout the cell cycle. There they are associated with a subcomplex of nucleoporins containing Nup53p, Nup170p, and Nup157p. The association of the Mad1p-Mad2p complex with the NPC requires Mad1p and is mediated in part by Nup53p. On activation of the spindle checkpoint, we detect changes in the interactions between these proteins, including the release of Mad2p (but not Mad1p) from the NPC and the accumulation of Mad2p at kinetochores. Accompanying these events is the Nup53p-dependent hyperphosphorylation of Mad1p. On the basis of these results and genetic analysis of double mutants, we propose a model in which Mad1p bound to a Nup53p-containing complex sequesters Mad2p at the NPC until its release by activation of the spindle checkpoint. Furthermore, we show that the association of Mad1p with the NPC is not passive and that it plays a role in nuclear transport.
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Affiliation(s)
- Tatiana Iouk
- Department of Cell Biology, University of Alberta, Edmonton, Alberta, T6G 2H7 Canada
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36
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Hartzog GA, Speer JL, Lindstrom DL. Transcript elongation on a nucleoprotein template. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1577:276-86. [PMID: 12213658 DOI: 10.1016/s0167-4781(02)00458-x] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Chromatin forms a general, repeating barrier to elongation of transcripts by eukaryotic RNA polymerases. Recent studies of nucleosome structure and histone modifications reveal a set of likely mechanisms for control of elongation through chromatin. Genetic and biochemical studies of transcription have identified a set of accessory factors for transcript elongation by RNA polymerase II (Pol II) that appear to function in the context of chromatin. The C-terminal repeated domain (CTD) of Pol II may also play a role in regulating elongation through chromatin.
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Affiliation(s)
- Grant A Hartzog
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, CA 95064, USA.
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37
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Basrai MA, Hieter P. Transcriptome analysis of Saccharomyces cerevisiae using serial analysis of gene expression. Methods Enzymol 2002; 350:414-44. [PMID: 12073327 DOI: 10.1016/s0076-6879(02)50977-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/25/2023]
Affiliation(s)
- Munira A Basrai
- Genetics Branch, National Cancer Institute, Bethesda, Maryland 20889, USA
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38
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Affiliation(s)
- J R Bone
- Department of Biochemistry and Molecular Biology, Box 117, University of Texas, M.D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030, USA
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39
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Kerscher O, Hieter P, Winey M, Basrai MA. Novel role for a Saccharomyces cerevisiae nucleoporin, Nup170p, in chromosome segregation. Genetics 2001; 157:1543-53. [PMID: 11290711 PMCID: PMC1461611 DOI: 10.1093/genetics/157.4.1543] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We determined that a mutation in the nucleoporin gene NUP170 leads to defects in chromosome transmission fidelity (ctf) and kinetochore integrity in Saccharomyces cerevisiae. A ctf mutant strain, termed s141, shows a transcription readthrough phenotype and stabilizes a dicentric chromosome fragment in two assays for kinetochore integrity. Previously, these assays led to the identification of two essential kinetochore components, Ctf13p and Ctf14p. Thus, s141 represents another ctf mutant involved in the maintenance of kinetochore integrity. We cloned and mapped the gene complementing the ctf mutation of s141 and showed that it is identical to the S. cerevisiae NUP170 gene. A deletion strain of NUP170 (nup170 Delta::HIS3) has a Ctf(-) phenotype similar to the s141 mutant (nup170-141) and also exhibits a kinetochore integrity defect. We identified a second nucleoporin, NUP157, a homologue of NUP170, as a suppressor of the Ctf(-) phenotype of nup170-141 and nup170 Delta::HIS3 strains. However, a deletion of NUP157 or several other nucleoporins did not affect chromosome segregation. Our data suggest that NUP170 encodes a specialized nucleoporin with a unique role in chromosome segregation and possibly kinetochore function.
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Affiliation(s)
- O Kerscher
- Department of Genetics, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20889, USA
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40
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Chen Y, Baker RE, Keith KC, Harris K, Stoler S, Fitzgerald-Hayes M. The N terminus of the centromere H3-like protein Cse4p performs an essential function distinct from that of the histone fold domain. Mol Cell Biol 2000; 20:7037-48. [PMID: 10958698 PMCID: PMC88778 DOI: 10.1128/mcb.20.18.7037-7048.2000] [Citation(s) in RCA: 123] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cse4p is an evolutionarily conserved histone H3-like protein that is thought to replace H3 in a specialized nucleosome at the yeast (Saccharomyces cerevisiae) centromere. All known yeast, worm, fly, and human centromere H3-like proteins have highly conserved C-terminal histone fold domains (HFD) but very different N termini. We have carried out a comprehensive and systematic mutagenesis of the Cse4p N terminus to analyze its function. Surprisingly, only a 33-amino-acid domain within the 130-amino-acid-long N terminus is required for Cse4p N-terminal function. The spacing of the essential N-terminal domain (END) relative to the HFD can be changed significantly without an apparent effect on Cse4p function. The END appears to be important for interactions between Cse4p and known kinetochore components, including the Ctf19p/Mcm21p/Okp1p complex. Genetic and biochemical evidence shows that Cse4p proteins interact with each other in vivo and that nonfunctional cse4 END and HFD mutant proteins can form functional mixed complexes. These results support different roles for the Cse4p N terminus and the HFD in centromere function and are consistent with the proposed Cse4p nucleosome model. The structure-function characteristics of the Cse4p N terminus are relevant to understanding how other H3-like proteins, such as the human homolog CENP-A, function in kinetochore assembly and chromosome segregation.
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Affiliation(s)
- Y Chen
- Department of Biochemistry and Molecular Biology, University of Massachusetts at Amherst, 01003, USA
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41
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Glowczewski L, Yang P, Kalashnikova T, Santisteban MS, Smith MM. Histone-histone interactions and centromere function. Mol Cell Biol 2000; 20:5700-11. [PMID: 10891506 PMCID: PMC86044 DOI: 10.1128/mcb.20.15.5700-5711.2000] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cse4p is a structural component of the core centromere of Saccharomyces cerevisiae and is a member of the conserved CENP-A family of specialized histone H3 variants. The histone H4 allele hhf1-20 confers defects in core centromere chromatin structure and mitotic chromosome transmission. We have proposed that Cse4p and histone H4 interact through their respective histone fold domains to assemble a nucleosome-like structure at centromeric DNA. To test this model, we targeted random mutations to the Cse4p histone fold domain and isolated three temperature-sensitive cse4 alleles in an unbiased genetic screen. Two of the cse4 alleles contain mutations at the Cse4p-H4 interface. One of these requires two widely separated mutations demonstrating long-range cooperative interactions in the structure. The third cse4 allele is mutated at its helix 2-helix 3 interface, a region required for homotypic H3 fold dimerization. Overexpression of wild-type Cse4p and histone H4 confer reciprocal allele-specific suppression of cse4 and hhf1 mutations, providing strong evidence for Cse4p-H4 protein interaction. Overexpression of histone H3 is dosage lethal in cse4 mutants, suggesting that histone H3 competes with Cse4p for histone H4 binding. However, the relative resistance of the Cse4p-H4 pathway to H3 interference argues that centromere chromatin assembly must be highly regulated.
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Affiliation(s)
- L Glowczewski
- Department of Microbiology and Cancer Center, University of Virginia, Charlottesville, Virginia 22908, USA
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42
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Ivanov D, Kwak YT, Guo J, Gaynor RB. Domains in the SPT5 protein that modulate its transcriptional regulatory properties. Mol Cell Biol 2000; 20:2970-83. [PMID: 10757782 PMCID: PMC85557 DOI: 10.1128/mcb.20.9.2970-2983.2000] [Citation(s) in RCA: 176] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
SPT5 and its binding partner SPT4 regulate transcriptional elongation by RNA polymerase II. SPT4 and SPT5 are involved in both 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB)-mediated transcriptional inhibition and the activation of transcriptional elongation by the human immunodeficiency virus type 1 (HIV-1) Tat protein. Recent data suggest that P-TEFb, which is composed of CDK9 and cyclin T1, is also critical in regulating transcriptional elongation by SPT4 and SPT5. In this study, we analyze the domains of SPT5 that regulate transcriptional elongation in the presence of either DRB or the HIV-1 Tat protein. We demonstrate that SPT5 domains that bind SPT4 and RNA polymerase II, in addition to a region in the C terminus of SPT5 that contains multiple heptad repeats and is designated CTR1, are critical for in vitro transcriptional repression by DRB and activation by the Tat protein. Furthermore, the SPT5 CTR1 domain is a substrate for P-TEFb phosphorylation. These results suggest that C-terminal repeats in SPT5, like those in the RNA polymerase II C-terminal domain, are sites for P-TEFb phosphorylation and function in modulating its transcriptional elongation properties.
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Affiliation(s)
- D Ivanov
- Division of Hematology-Oncology, Department of Medicine, Harold Simmons Cancer Center, University of Texas Southwestern Medical Center, Dallas, Texas 75235-8594, USA
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43
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Chiang PW, Wei WL, Gibson K, Bodmer R, Kurnit DM. A fluorescent quantitative PCR approach to map gene deletions in the Drosophila genome. Genetics 1999; 153:1313-6. [PMID: 10545461 PMCID: PMC1460813 DOI: 10.1093/genetics/153.3.1313] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
We report the application of TaqMan quantitative PCR (QPCR) to map Drosophila chromosome deficiencies by discrimination of twofold copy number differences. For a model system, we used this technology to confirm the X chromosomal mapping of Dspt6 given the autosomal mapping of Dspt4. We then used this technique on both preexisting deletion mutant flies and flies that we generated with deletions to demonstrate the presence or absence of Dspt6, Dspt4, and swa in various deletion mutant flies. In contrast with in situ hybridization studies, QPCR both vitiates the need to do these more intricate studies, and it is more accurate as the site of deletion can be known down to the 10(2)-bp level. We then successfully applied the technique to the analysis of transcription, demonstrating that the amount of Dspt6 or Dspt4 transcriptional product depended directly on the dosage of the Dspt6 or Dspt4 gene, respectively. The rapidity and precision of this method demonstrates its applicability in Drosophila genetics, the rapid and accurate mapping of Drosophila deletion mutants.
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Affiliation(s)
- P W Chiang
- Department of Pediatrics, University of Michigan, Ann Arbor, Michigan 48109-0650, USA.
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44
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Basrai MA, Velculescu VE, Kinzler KW, Hieter P. NORF5/HUG1 is a component of the MEC1-mediated checkpoint response to DNA damage and replication arrest in Saccharomyces cerevisiae. Mol Cell Biol 1999; 19:7041-9. [PMID: 10490641 PMCID: PMC84699 DOI: 10.1128/mcb.19.10.7041] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Analysis of global gene expression in Saccharomyces cerevisiae by the serial analysis of gene expression technique has permitted the identification of at least 302 previously unidentified transcripts from nonannotated open reading frames (NORFs). Transcription of one of these, NORF5/HUG1 (hydroxyurea and UV and gamma radiation induced), is induced by DNA damage, and this induction requires MEC1, a homolog of the ataxia telangiectasia mutated (ATM) gene. DNA damage-specific induction of HUG1, which is independent of the cell cycle stage, is due to the alleviation of repression by the Crt1p-Ssn6p-Tup1p complex. Overexpression of HUG1 is lethal in combination with a mec1 mutation in the presence of DNA damage or replication arrest, whereas a deletion of HUG1 rescues the lethality due to a mec1 null allele. HUG1 is the first example of a NORF with important biological functional properties and defines a novel component of the MEC1 checkpoint pathway.
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Affiliation(s)
- M A Basrai
- Department of Molecular Biology & Genetics, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
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45
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Zheng L, Chen Y, Lee WH. Hec1p, an evolutionarily conserved coiled-coil protein, modulates chromosome segregation through interaction with SMC proteins. Mol Cell Biol 1999; 19:5417-28. [PMID: 10409732 PMCID: PMC84384 DOI: 10.1128/mcb.19.8.5417] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/1999] [Accepted: 05/05/1999] [Indexed: 11/20/2022] Open
Abstract
hsHec1p, a Homo sapiens coiled-coil-enriched protein, plays an important role in M-phase progression in mammalian cells. A Saccharomyces cerevisiae protein, identical to Tid3p/Ndc80p and here designated scHec1p, has similarities in structure and biological function to hsHec1p. Budding yeast cells deleted in the scHEC1/NDC80 allele are not viable, but this lethal phenotype can be rescued by hsHEC1 under control of the endogenous scHEC1 promoter. At the nonpermissive temperature, significant mitotic delay, chromosomal missegregation, and decreased viability were observed in yeast cells with temperature-sensitive (ts) alleles of hsHEC1. In the hshec1-113 ts mutant, we found a single-point mutation changing Trp395 to a stop codon, which resulted in the expression of a C-terminally truncated 45-kDa protein. The binding of this mutated protein, hshec1-113p, to five identified hsHec1p-associated proteins was unchanged, while its binding to human SMC1 protein and yeast Smc1p was ts. Hec1p also interacts with Smc2p, and the binding of the mutated hshec1-113p to Smc2p was not ts. Overexpression of either hsHEC1 or scHEC1 suppressed the lethal phenotype of smc1-2 and smc2-6 at nonpermissive temperatures, suggesting that the interactions between Hec1p and Smc1p and -2p are biologically significant. These results suggest that Hec1 proteins play a critical role in modulating chromosomal segregation, in part, through their interactions with SMC proteins.
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Affiliation(s)
- L Zheng
- Department of Molecular Medicine, Institute of Biotechnology, University of Texas Health Science Center San Antonio, San Antonio, Texas 78245, USA
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46
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Dobie KW, Hari KL, Maggert KA, Karpen GH. Centromere proteins and chromosome inheritance: a complex affair. Curr Opin Genet Dev 1999; 9:206-17. [PMID: 10322137 DOI: 10.1016/s0959-437x(99)80031-8] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Centromeres and the associated kinetochores are involved in essential aspects of chromosome transmission. Recent advances have included the identification and understanding of proteins that have a pivotal role in centromere structure, kinetochore formation, and the coordination of chromosome inheritance with the cell cycle in several organisms. A picture is beginning to emerge of the centromere-kinetechore as a complex and dynamic structure with conservation of function at the protein level across diverse species.
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Affiliation(s)
- K W Dobie
- Molecular Biology and Virology Laboratory, Salk Institute for Biological Studies, La Jolla, California 92037, USA.
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Skibbens RV, Hieter P. Kinetochores and the checkpoint mechanism that monitors for defects in the chromosome segregation machinery. Annu Rev Genet 1999; 32:307-37. [PMID: 9928483 DOI: 10.1146/annurev.genet.32.1.307] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Whether we consider the division of the simplest unicellular organisms into two daughter cells or the generation of haploid gametes by the most complex eukaryotes, no two processes secure the continuance of life more than the proper replication and segregation of the genetic material. The cell cycle, marked in part by the periodic rise and fall of cyclin-dependent kinase (CDK) activities, is the means by which these two processes are separated. DNA damage and mistakes in chromosome segregation are costly, so nature has further devised elaborate checkpoint mechanisms that halt cell cycle progression, allowing time for repairs or corrections. In this article, we review the mitotic checkpoint mechanism that responds to defects in the chromosome segregation machinery and arrests cells in mitosis prior to anaphase onset. At opposite ends of this pathway are the kinetochore, where many checkpoint proteins reside, and the anaphase-promoting complex (APC), the metaphase-to-interphase transition regulator. Throughout this review we focus on budding yeast but reference parallel processes found in other organisms.
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Affiliation(s)
- R V Skibbens
- Carnegie Institute of Washington, Department of Embryology, Baltimore, Maryland 21210, USA.
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Poddar A, Roy N, Sinha P. MCM21 and MCM22, two novel genes of the yeast Saccharomyces cerevisiae are required for chromosome transmission. Mol Microbiol 1999; 31:349-60. [PMID: 9987135 DOI: 10.1046/j.1365-2958.1999.01179.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The minichromosome maintenance genes, MCM21 and MCM22, have been cloned and are shown to code for the ORFs YDR318W and YJR135C respectively. Mutations in these genes caused a decrease in the stability of the minichromosome. This decrease in stability was associated with an increase in the copy number of the minichromosome in cells carrying it. Small circular dicentric plasmids were maintained relatively stably and structurally intact in the mutants compared with the wild-type strain. In the latter, such plasmids were mitotically unstable and, upon recovery, showed frequent rearrangements of their DNA. A centromere offered less obstruction to transcription in mutant cells than in the wild type, showing that both these mutants had a more relaxed kinetochore assembly. The mutant strains showed elevated rates of chromosome loss but not those of recombination. Both the mutations caused the cells to display a higher sensitivity towards the anti-mitotic drug benomyl. All these observations suggest that MCM21 and MCM22 are important for chromosome segregation with a potential role in kinetochore function. These genes are non-essential, as their deletions from chromosomes did not cause loss of cell viability. However, exponentially growing mutant cells carrying the deletion of the MCM21 gene had a significant population of large-budded cells with a single nucleus at the neck. Furthermore, the DNA content of these cells showed a shift towards 2N, suggesting a temporary pause of cells in G2 or in an early phase of mitosis. The mcm21 and mcm22 mutations do not show synthetic lethality or any further enhancement of growth defects, implying that they could be carrying out non-overlapping functions in chromosome segregation.
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Affiliation(s)
- A Poddar
- Department of Biochemistry, Bose Institute, Calcutta, India
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Abstract
The synthesis of mature and functional messenger RNA by eukaryotic RNA polymerase II (Pol II) is a complex, multistage process requiring the cooperative action of many cellular proteins. This process, referred to collectively as the transcription cycle, proceeds via five stages: preinitiation, initiation, promoter clearance, elongation, and termination. During the past few years, fundamental studies of the elongation stage of transcription have demonstrated the existence of several families of Pol II elongation factors governing the activity of Pol II. It is now clear that the elongation stage of transcription is a critical stage for the regulation of gene expression. In fact, two of these elongation factors, ELL and elongin, have been implicated in human cancer. This article will review the proteins involved in the regulation of the elongation stage of transcription by Pol II, describing the recent experimental findings that have propelled vigorous research on the properties and function of the elongating RNA polymerase II. --Shilatifard, A. Factors regulating the transcriptional elongation activity of RNA polymerase II.
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Affiliation(s)
- A Shilatifard
- Department of Biochemistry, St. Louis University School of Medicine, St. Louis, Missouri 63104, USA.
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Tsuchiya E, Hosotani T, Miyakawa T. A mutation in NPS1/STH1, an essential gene encoding a component of a novel chromatin-remodeling complex RSC, alters the chromatin structure of Saccharomyces cerevisiae centromeres. Nucleic Acids Res 1998; 26:3286-92. [PMID: 9628931 PMCID: PMC147684 DOI: 10.1093/nar/26.13.3286] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The NPS1/STH1 gene encodes a nuclear protein essential for the progression of G2/M phase in Saccharomyces cerevisiae . Nps1p shares homology to Snf2/Swi2p, a subunit of a protein complex known as the SNF/SWI complex. Recently, Nps1p was found to be a component of a protein complex termed RSC (3) essential for mitotic growth, whereas its function is unknown. We isolated a temperature-sensitive mutant allele of NPS1 , nps1-105, and found that the mutation increases the sensitivity to thiabendazole (TBZ). At the restrictive temperature, nps1-105 arrested at the G2/M phase in MAD1-dependent manner and missegregated the mini-chromosome with higher frequency than the wild type cells. The nuclease digestion of the chromatin of the mutant cells revealed that the mutation causes the alteration of the chromatin structure around centromeres at the restrictive temperature. The results suggested that, in the nps1-105 mutant, impaired chromatin structure surrounding centromeres may lead to an impairment of kinetochore function and the cells arrest at G2/M phase through the spindle-assembly checkpoint system.
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Affiliation(s)
- E Tsuchiya
- Department of Fermentation Technology, Faculty of Engineering, Hiroshima University, Kagamiyama, Higashi-Hiroshima 739-8527, Japan.
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