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Stress-induced multimerization of MYC shields stalled replication forks from RNA Polymerase

ABSTRACT: Oncoproteins of the MYC family drive the development of numerous human tumors1-4. In unperturbed cells, MYC proteins bind to virtually all active promoters and control transcription by RNA Polymerase II (RNAPII)2,3,5,6. MYC proteins can also coordinate transcription with DNA replication7-9 and promote the repair of transcription-associated DNA damage10, but how they exert these mechanistically diverse functions is unknown. Here we show that MYC dissociates from most of its binding sites in promoters and forms stable multimeric shell-like structures in response to perturbation of transcription elongation, mRNA splicing, or DNA replication. MYC multimers recruit interacting proteins that can promote transcription termination into their shells. Intriguingly, MYC multimers accumulate on chromatin immediately adjacent to stalled replication forks and surround the FANCD2, ATR and BRCA1 proteins, which are located at stalled forks11,12. MYC multimers accumulate ubiquitylated proteins and their formation depends on the HUWE1 ubiquitin ligase10,13. In response to replication stress, HUWE1 and MYC limit phosphorylation of the single-strand binding protein, RPA. We propose that localised multimerisation of MYC creates a transcription termination zone around stalled replication forks that limits checkpoint signalling in response to transcriptional and replication stress, allowing tumor cells to actively proliferate under stressful conditions

ORGANISM(S): Homo sapiens

PROVIDER: GSE183094 | GEO | 2022/09/08

REPOSITORIES: GEO

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Project description:Background: Chromatin remodeling complexes facilitate the access of enzymes that mediate transcription, replication or repair of DNA by modulating nucleosome position and/or composition. Ino80 is the DNA-dependent Snf2-like ATPase subunit of a complex whose nucleosome remodeling activity requires actin-related proteins, Arp4, Arp5 and Arp8, as well as two RuvB-like DNA helicase subunits. Budding yeast mutants deficient for Ino80 function are not only hypersensitive to reagents that induce DNA double strand breaks, but also to those that impair replication fork progression. Results: To understand why ino80 mutants are sensitive to agents that perturb DNA replication, we used chromatin immunoprecipitation to map the binding sites of the Ino80 chromatin remodeling complex on four budding yeast chromosomes. We found that Ino80 and Arp5 binding sites coincide with origins of DNA replication and tRNA genes. In addition, Ino80 was bound at 67% of the promoters of genes that are sensitive to ino80 mutation. When replication forks were arrested near origins in the presence of hydroxyurea (HU), the presence of the Ino80 complex at stalled forks and at unfired origins increased dramatically. Importantly, the resumption of DNA replication after release from a HU block was impaired in the absence of Ino80 activity. Mutant cells accumulated double-strand breaks as they attempted to restart replication. Consistently, ino80-deficient cells, although proficient for checkpoint activation, delay recovery from the checkpoint response. Conclusions: The Ino80 chromatin remodeling complex is enriched at stalled replication forks where it promotes the resumption of replication upon recovery from fork arrest. Keywords: ChIP-chip • The goal of the experiment Genome-wide localization of Ino80 on chromosome in Saccharomyces cerevisiae • Keywords DNA replication, Saccharomyces cerevisiae, Genome tilling array (chromosome III, IV, V, VI) • Experimental factor Distribution of Ino80 in random culture Distribution of Ino80 in G1 phase Distribution of Ino80 in early S phase • Experimental design ChIP analyses: W303 background cells expressing Myc-tagged Ino80 were used for the ChIP using anti-Myc monoclonal antibody (9E11). ChIP-chip analyses: In all cases, hybridization data for ChIP fraction was compared with WCE (whole cell extract) fraction. Saccharomyces cerevisiae affymetrix genome tiling array (SC3456a520015F for chromosome III, IV, V, VI) was used. • Quality control steps taken Confirmation of several loci by quantitative real time PCR.

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Stress-induced multimerization of MYC shields stalled replication forks from RNA Polymerase

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