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 (RNA Recognition Motifs) 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.