RECQL5 is one of the five human
RecQ helicases, involved in the maintenance of genomic integrity. While much insight has been gained into the function of the Werner (WRN) and
Bloom syndrome proteins (BLM), little is known about RECQL5. We have analyzed the recruitment and retention dynamics of RECQL5 at
laser-induced
DNA double strand breaks (DSBs) relative to other human
RecQ helicases. RECQL5-depleted cells accumulate persistent 53BP1 foci followed by γ-irradiation, indicating a potential role of RECQL5 in the processing of DSBs. Real time imaging of live cells using confocal
laser microscopy shows that RECQL5 is recruited early to
laser-induced DSBs and remains for a shorter duration than BLM and WRN, but persist longer than RECQL4. These studies illustrate the differential involvement of
RecQ helicases in the
DSB repair process. Mapping of domains within RECQL5 that are necessary for recruitment to DSBs revealed that both the helicase and KIX domains are required for DNA damage recognition and stable association of RECQL5 to the
DSB sites. Previous studies have shown that MRE11 is essential for the recruitment of RECQL5 to the
DSB sites. Here we show that the recruitment of RECQL5 does not depend on the
exonuclease activity of MRE11 or on active transcription by
RNA polymerase II, one of the prominent interacting partners of RECQL5. Also, the recruitment of RECQL5 to
laser-induced damage sites is independent of the presence of other DNA damage signaling and repair
proteins BLM, WRN and ATM.