Abstract
SummaryModulating chromatin through histone methylation orchestrates numerous cellular processes. SETD2-dependent trimethylation of histone H3K36 is associated with active transcription. Here, we define a role for H3K36 trimethylation in homologous recombination (HR) repair in human cells. We find that depleting SETD2 generates a mutation signature resembling RAD51 depletion at I-SceI-induced DNA double-strand break (DSB) sites, with significantly increased deletions arising through microhomology-mediated end-joining. We establish a presynaptic role for SETD2 methyltransferase in HR, where it facilitates the recruitment of C-terminal binding protein interacting protein (CtIP) and promotes DSB resection, allowing Replication Protein A (RPA) and RAD51 binding to DNA damage sites. Furthermore, reducing H3K36me3 levels by overexpressing KDM4A/JMJD2A, an oncogene and H3K36me3/2 demethylase, or an H3.3K36M transgene also reduces HR repair events. We propose that error-free HR repair within H3K36me3-decorated transcriptionally active genomic regions promotes cell homeostasis. Moreover, these findings provide insights as to why oncogenic mutations cluster within the H3K36me3 axis.
Highlights
DNA double-stranded breaks (DSBs) are potentially lethal lesions if unrepaired, and their misrepair can give rise to genome instability, a hallmark of cancer (Jeggo and Lavin, 2009)
We find that depleting SETD2 generates a mutation signature resembling RAD51 depletion at Intron-encoded endonuclease from Saccharomyces cerevisiae (I-SceI)-induced DNA doublestrand break (DSB) sites, with significantly increased deletions arising through microhomology-mediated end-joining
We establish a presynaptic role for SETD2 methyltransferase in homologous recombination (HR), where it facilitates the recruitment of C-terminal binding protein interacting protein (CtIP) and promotes DSB resection, allowing Replication Protein A (RPA) and RAD51 binding to DNA damage sites
Summary
DNA double-stranded breaks (DSBs) are potentially lethal lesions if unrepaired, and their misrepair can give rise to genome instability, a hallmark of cancer (Jeggo and Lavin, 2009). To maintain genome stability in response to such lesions, cells employ either homologous recombination (HR) or nonhomologous end-joining (NHEJ) pathways to repair DSBs. HR is initiated by 50 end resection to generate a 30 single-stranded DNA (ssDNA) overhang. Resection is a two-step process initiated by removing a short oligonucleotide through the activities of the Mre11-Rad50-Nbs (MRN) complex and CtIP. Damaged ends are processed and subsequently joined by the Ligase 4 (Lig4), XRCC4, XLF complex in a template-independent manner, which can lead to inaccurate repair (Lieber, 2010). DSBs may be repaired through alternative endjoining pathways, such as microhomology-mediated end-joining (MMEJ), which do not require Ku or Lig. Like HR, MMEJ is initiated by resection, and end-joining is mediated through annealing of short direct repeats of microhomology. MMEJ leads to deletions and is frequently associated with chromosomal rearrangements (McVey and Lee, 2008)
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