Padeken, JanJanPadekenZeller, PeterPeterZellerTowbin, Benjamin DanielBenjamin DanielTowbin0000-0001-7046-1257Katic, IskraIskraKaticKalck, VeroniqueVeroniqueKalckMethot, Stephen PStephen PMethotGasser, Susan MSusan MGasser2024-10-282024-10-282019-04-01https://boris-portal.unibe.ch/handle/20.500.12422/180423has two histone H3 Lys9 methyltransferases, MET-2 (SETDB1 homolog) and SET-25 (G9a/SUV39H1 related). In worms, we found simple repeat sequences primarily marked by H3K9me2, while transposable elements and silent tissue-specific genes bear H3K9me3. RNA sequencing (RNA-seq) in histone methyltransferase (HMT) mutants shows that MET-2-mediated H3K9me2 is necessary for satellite repeat repression, while SET-25 silences a subset of transposable elements and tissue-specific genes through H3K9me3. A genome-wide synthetic lethality screen showed that RNA processing, nuclear RNA degradation, the BRCA1/BARD1 complex, and factors mediating replication stress survival are necessary for germline viability in worms lacking MET-2 but not SET-25. Unlike mutants, -null worms accumulated satellite repeat transcripts, which form RNA:DNA hybrids on repetitive sequences, additively with the loss of BRCA1 or BARD1. BRCA1/BARD1-mediated H2A ubiquitination and MET-2 deposited H3K9me2 on satellite repeats are partially interdependent, suggesting both that the loss of silencing generates BRCA-recruiting DNA damage and that BRCA1 recruitment by damage helps silence repeats. The artificial induction of MSAT1 transcripts can itself trigger damage-induced germline lethality in a wild-type background, arguing that the synthetic sterility upon BRCA1/BARD1 and H3K9me2 loss is directly linked to the DNA damage provoked by unscheduled satellite repeat transcription.enBRCA1 complex DNA repeats RNA:DNA hybrids genome instability heterochromatin histone H3K9 methylation satellite repeats transcriptional silencing500 - Science::570 - Life sciences; biologyarticle10.7892/boris.1306133080422810.1101/gad.322495.118