Saccharomyces cerevisiae Hrq1 helicase preferentially binds and unwinds displacement-loop structures

초록

Hrq1 is a novel member of RecQ helicase family recently identified by bioinformatic analyses. It is highly conserved in fungal genomes and most homologous to human RECQL4. We have reported that Hrq1 is an active helicase stimulated by the presence of a long 3’-single stranded DNA. Here we show Hrq1 displayed structure-specific DNA-binding property. It preferentially bound to bubble and displacement-loop structures. In addition, it was able to resolve displacement-loop structures but hardly unwound bubble DNA substrates. The resolution of displacement-loop was strongly stimulated by the presence of 3’-tail. Consistent with a recent report that human RECQL4 localizes at telomere, Hrq1 was found to more tightly bind to yeast telomeric sequences than random sequences. Moreover, DNA substrates with telomeric sequences were more susceptible to unwinding reaction by Hrq1. Our results indicate that Hrq1 is able to function in various DNA metabolisms for maintenance of genome stability that deserves further characterization to expand our understanding of RecQ helicases.