The RRM domains of PARP14 mediate replication fork degradation in BRCA2-deficient cells

Degradation of reversed replication forks by nucleases has emerged as a major mechanism of chemosensitivity in BRCA-deficient cells. We previously showed that the mono-ADP-ribosyltransferase PARP14 regulates MRE11 recruitment to reversed replication forks to promote their degradation. This results in genomic instability in BRCA-deficient cells. While it has been shown that PARP14-mediated recruitment of MRE11 to reversed forks promotes their degradation and collapse, how PARP14 binds to nascent DNA is unknown. Here, we show that, in BRCA-deficient cells, PARP14 is recruited to nascent DNA at reversed replication forks via its RRM (<ani:underline>R</ani:underline>NA <ani:underline>R</ani:underline>ecognition <ani:underline>M</ani:underline>otifs) domains. We reveal that the RRM domains are necessary for the recruitment of MRE11 to reversed forks to promote nascent strand degradation at stalled replication forks in BRCA2-deficient cells. We also show that these domains are essential for replication stress-induced double-strand break formation in these cells. Our work furthers the understanding of nuclease recruitment and engagement at stalled forks to regulate genomic stability.