Coordination between transcription and replication is crucial in the maintenance of genome integrity. Disturbance of these processes leads to accumulation of aberrant DNA:RNA hybrids (R‐loops) that, if unresolved, generate DNA damage and genomic instability. Here we report a novel, unexpected role for the nucleopore‐associated mRNA export factor Ddx19 in removing nuclear R‐loops formed upon replication stress or DNA damage. We show, in live cells, that Ddx19 transiently relocalizes from the nucleopore to the nucleus upon DNA damage, in an ATR/Chk1‐dependent manner, and that Ddx19 nuclear relocalization is required to clear R‐loops. Ddx19 depletion induces R‐loop accumulation, proliferation‐dependent DNA damage and defects in replication fork progression. Further, we show that Ddx19 resolves R‐loops in vitro via its helicase activity. Furthermore, mutation of a residue phosphorylated by Chk1 in Ddx19 disrupts its interaction with Nup214 and allows its nuclear relocalization. Finally, we show that Ddx19 operates in resolving R‐loops independently of the RNA helicase senataxin. Altogether these observations put forward a novel, ATR‐dependent function for Ddx19 in R‐loop metabolism to preserve genome integrity in mammalian cells.
The helicase Ddx19, which functions as a nucleopore‐associated mRNA export factor, has an unexpected additional nuclear role in resolving R‐loops and maintaining genome stability upon DNA damage or replication stress.
Ddx19 translocates into the nucleus upon DNA damage.
Ddx19 nuclear translocation is mediated by the ATR‐Chk1 signaling pathway.
Recombinant Ddx19 displays RNA:DNA helicase and R‐loop‐resolving activity in vitro.
Ddx19 downregulation generates nuclear R‐loops and DNA double‐strand breaks.
Ddx19 function in R‐loop metabolism is independent of the RNA helicase senataxin.
- Received June 29, 2016.
- Revision received February 10, 2017.
- Accepted February 14, 2017.
- © 2017 The Authors
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