Unknown,Transcriptomics,Genomics,Proteomics

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The ATP-dependent chromatin remodeling enzyme Fun30 represses transcription by sliding promoter proximal nucleosomes [seq]

ABSTRACT: The evolutionarily conserved ATP-dependent chromatin remodeling enzyme Fun30 has recently been shown to play important roles in heterochromatin silencing and DNA repair. However, how Fun30 remodels nucleosomes is not clear. Here we report a nucleosome sliding activity of Fun30 and its role in transcriptional repression. We observed that Fun30 repressed the expression of genes involved in amino acid and carbohydrate metabolism, the stress response, and meiosis. In addition, Fun30 was localized at the 5M-bM-^@M-2 and 3M-bM-^@M-2 ends of genes and within the open reading frames of its targets. Consistent with its role in gene repression, we observed that Fun30-target genes lacked histone modifications often associated with gene activation and showed an increased level of ubiquitinated histone H2B. Furthermore, genome-wide nucleosome mapping analysis revealed that the length of the nucleosome-free region at the 5M-bM-^@M-2 end of a subset of genes was changed in Fun30-depleted cells. In addition, the positions of the -1, +2 and +3 nucleosomes at the 5M-bM-^@M-2 end of target genes were significantly shifted, while position of the +1 nucleosome remained largely unchanged in the fun30M-NM-^T mutant. Finally, we demonstrated that affinity purified single-component Fun30 exhibited nucleosome sliding activity in an ATP-dependent manner. These results define a role for Fun30 in regulation of transcription and indicate that Fun30 remodels chromatin at the 5M-bM-^@M-2 end of genes by sliding promoter proximal nucleosomes. Micrococcal nuclease digested mononucleosome DNA from wild type and fun30D cells were sequenced by illumina Genome Analyzer. Genome-wide nucleosome positioning and occupancy were analyzed.

ORGANISM(S): Saccharomyces cerevisiae

SUBMITTER: Wei-Hua Wu

PROVIDER: E-GEOD-48562 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:SWI/SNF-family chromatin remodelling complexes conduct nucleosome sliding and ejection to provide DNA-binding proteins access to their sites in chromatin. RSC is an essential and abundant SWI/SNF-family chromatin remodeller from S. cerevisiae that both slides and ejects nucleosomes. However, how ejection versus sliding is chosen, regulated and implemented by any remodeller remains largely unknown. The RSC catalytic subunit Sth1 conducts ATP-dependent DNA translocation, pumping DNA around the nucleosome, providing a property that might underlie both sliding and ejection. Sth1 shares with other SWI/SNF-family ATPases direct binding to two nuclear actin-related proteins (ARPs), but how ARPs impact DNA translocation, sliding and ejection is unknown. Here, we reveal that nucleosome ejection by RSC requires ARPs, and that ARPs improve ‘coupling’ – the efficiency of DNA translocation by Sth1 relative to ATP hydrolysis – thus, enhancing DNA translocation. We further characterize two domains within Sth1 (termed PTH and P1), showing they separately regulate ATP hydrolysis or ‘coupling’, respectively. Interestingly, gain-of-function PTH or P1 mutations suppress arpΔ lethality, and improve ATPase or coupling activities, enabling Sth1 to efficiently slide and eject nucleosomes without ARPs. Moreover, PTH mutations greatly improved DNA translocation velocity. Overall, our results provide a logic for regulating nucleosome sliding versus ejection: both modes involve DNA translocation, but ejection requires a higher magnitude. Here, low-to-moderate ATPase and coupling activity integrate to confer low-to-moderate sliding, whereas high ATPase and/or coupling combine to provide efficient and rapid DNA translocation, consistent with the simultaneous rupture of multiple histone-DNA contacts, causing histone loss/ejection. Our discovery of an ARP module and regulatory domains that regulate sliding and ejection suggests a mechanistic platform through which activators and histone epitopes may guide the remodelling outcome of SWI/SNF-family chromatin remodellers.

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The ATP-dependent chromatin remodeling enzyme Fun30 represses transcription by sliding promoter proximal nucleosomes [seq]

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