Polymerase -helicase efficiently unwinds DNA and RNA-DNA hybrids

POLQ is a unique multifunctional replication and repair gene that encodes for a N-terminal superfamily 2 helicase and a C-terminal A-family polymerase. Although the function of the polymerase domain has been investigated, little is understood regarding the helicase domain. Multiple studies have reported that polymerase -helicase (Pol-helicase) is unable to unwind DNA. However, it exhibits ATPase activity that is stimulated by single-stranded DNA, which presents a biochemical conundrum. In contrast to previous reports, we demonstrate that Pol-helicase (residues 1-894) efficiently unwinds DNA with 3-5 polarity, including DNA with 3 or 5 overhangs, blunt-ended DNA, and replication forks. Pol-helicase also efficiently unwinds RNA-DNA hybrids and exhibits a preference for unwinding the lagging strand at replication forks, similar to related HELQ helicase. Finally, we find that Pol-helicase can facilitate strand displacement synthesis by Pol-polymerase, suggesting a plausible function for the helicase domain. Taken together, these findings indicate nucleic acid unwinding as a relevant activity for Pol in replication repair.