multifunctional helicase

ScPif1 DNA helicase is the prototypical member of a 5′-to-3 ′ helicase superfamily conserved from bac-teria to human and plays various roles in the main-tenance of genomic homeostasis. While many stud-ies have been performed with eukaryotic Pif1 heli-cases, including yeast and human Pif1 proteins, the potential functions and biochemical properties of prokaryotic Pif1 helicases remain largely unknown. Here, we report the expression, purification and bio-chemical analysis of Pif1 helicase from Bacteroides sp. 3 1 23 (BsPif1). BsPif1 binds to a large panel of DNA substrates and, in particular, efficiently un-winds partial duplex DNAs with 5′-overhang, fork-like substrates, D-loop and flap-like substrates, sug-gesting that BsPif1 may act at stalled DNA replica-tion forks and enhance Okazaki fragment maturation. Like its eukaryotic homologues, BsPif1 resolves R-loop structures and unwinds DNA–RNA hybrids. Fur-thermore, BsPif1 efficiently unfolds G-quadruplexes and disrupts nucleoprotein complexes. Altogether, these results highlight that prokaryotic Pif1 helicases may resolve common issues that arise during DNA transactions. Interestingly, we found that BsPif1 is different from yeast Pif1, but resembles more human Pif1 with regard to substrate specificity, helicase ac-tivity and mode of action. These findings are dis-cussed in the context of the possible functions of prokaryotic Pif1 helicases in vivo