RECQL4 Promotes DNA End Resection in Repair of DNA Double-Strand Breaks

Abstract

SUMMARY The RecQ helicase RECQL4, mutated in Rothmund-Thomson syndrome, regulates genome stability, aging and cancer. Here, we identify a crucial role for RECQL4 in DNA end resection, which is the initial and an essential step of homologous recombination (HR)-dependent DNA double-strand break repair (DSBR). Depletion of RECQL4 severely reduces HR-mediated repair and 5’ end resection in vivo. RECQL4 physically interacts with MRE11-RAD50-NBS1 (MRN), which senses DSBs and initiates DNA end resection with CtIP. The MRE11 exonuclease regulates the retention of RECQL4 at laser-induced DSBs. RECQL4 also directly interacts with CtIP via its N-terminal domain and promotes CtIP recruitment to the MRN complex at DSBs. Moreover, inactivation of RECQL4’s helicase activity impairs DNA end processing and HR-dependent DSBR without affecting its interaction with MRE11 and CtIP, suggesting an important role for RECQL4’s unwinding activity in the process. Thus, we report here that RECQL4 is an important participant in HR-dependent DSBR.

Dna2 initiates resection at clean DNA double-strand breaks

“…The requirement of RPA in CtIP–MRN-mediated resection initiation is surprising, as Sae2–MRX or CtIP–MRN can directly clip 5′ strand DNA at blocked DSBs in the absence of RPA in reconstituted reactions (41,42). However, a role of RPA in the CtIP–MRN-mediated resection initiation is consistent with the requirement of DNA helicases such as WRN (and potentially RECQL4) for the pathway (Supplementary Figure S5F) (107). RPA may stimulate the activity of CtIP–MRN or help to present ssDNA substrate after end unwinding for CtIP–MRN-mediated cleavage.…”

“…Interestingly, depletion of WRN from the extract also dramatically inhibited the generation of long cleavage products in the presence or in the absence of Dna2 (Supplementary Figure S5E and F), suggesting that WRN is also involved in the CtIP–MRN pathway of resection initiation. A recent study has shown that the helicase activity of RECQL4 is required for CtIP–MRN-dependent resection in human cells (107). Future studies are needed to further define the potential role of WRN and RECQL4 in CtIP–MRN-mediated resection initiation at clean DSBs.…”

Holliday junction trap shows how cells use recombination and a junction-guardian role of RecQ helicase

“…We suggest that at least one consequence of overexpressed RAD51 in tumors could be increased RFs, which are genome-destabilizing and cause genome evolution that could drive the cancer state ( 73 ), and that BLM and RECQL4 may prevent RF-HJs, whereas EME1 and GEN1 may cleave the RFs, creating DSB ends that cycle through repair and replication. Purified BLM can promote fork regression in solution ( 74 ), and RECQL4 promotes HR-HJs ( 26 ). Perhaps they also prevent RF-HJs in cells.…”

The MRE11–RAD50–NBS1 Complex Conducts the Orchestration of Damage Signaling and Outcomes to Stress in DNA Replication and Repair

“…Via interaction with the MRN complex or CtIP, extended DNA resection is stimulated by additional enzymes, including RECQL4 helicase and possibly by EXD2 exonuclease (101, 102), which has alternatively been localized to the cytoplasm and regulates translation in mitochondria (103). Regardless, the biochemistry for these regulating partners suggests changes in protein–DNA interaction stability and off rates.…”