Chromatin-associated MRN complex protects highly transcribing genes from genomic instability

Abstract

The MRN-MDC1 complex plays a central role in the DNA damage response (DDR) and repair.Using Proteomics of Isolated Chromatin Fragments (PICh), we identified DDR factors, such as MDC1, among those that become highly associated with a genomic locus upon transcriptional activation. Purification of endogenous MDC1, in the absence of exogenous DNA damage, revealed its interaction with factors involved in gene expression and co-transcriptional RNA processing, in addition to DDR factors. ChIP-seq analysis showed that MDC1 interacting factors, MRE11 and NBS1 subunits of MRN, were co-localized throughout the genome and notably at TSSs and gene bodies of actively transcribing genes. Blockade of transcriptional elongation showed that binding of MRN was dependent on the RNAPII transcriptional complex rather than transcription per se. Depletion of MRN increased RNAPII abundance at TSSs and gene bodies of MRE11/NBS1-bound genes. Prolonged exposure of cells to either MRE11-or NBS1-depletion led to single nucleotide polymorphism formation across actively transcribing, MRE11 or NBS1 target genes. These data support a model by which association of the MRN complex with the transcriptional machinery constitutively scans active genes for transcription-induced DNA damage to preserve the integrity of the coding genome.

Chromatin-associated YTHDC1 coordinates heat-induced reprogramming of gene expression

“…6,7 We then determined the transcriptional status of the genes bound by YTHDC1, by considering their association with RNAPII, in both NHS and HS conditions. 48 Among YTHDC1 genomic targets, approximately 75% were also associated with RNAPII, under both NHS and HS conditions (Figure S2E). Conversely, less than 25% of the RNAPII-associated genes were enriched in YTHDC1 under NHS and HS conditions (Figure S2F).…”