Abstract
In the yeast Saccharomyces cerevisiae, the PIF1 family helicases Pif1 and Rrm3 aid in the maintenance of nuclear and mitochondrial genome stability. Despite great progress in understanding the roles of these enzymes as a whole, the functions of the N- and C-terminal domains that flank their central helicase core remain unclear. Here, we characterized the biochemical activities of the Thermotoga elfii PIF1 helicase (TePif1), which contains a C-terminal WYL domain. As is typical of helicases from thermophilic organisms, recombinant TePif1 was amenable to over-expression and purification, thermostable in vitro, and displayed activities similar to its better-studied eukaryotic homologs. We also found that the WYL domain was necessary for high affinity single-stranded DNA (ssDNA) binding and impacted both ATPase and helicase activities. Our results indicate that TePif1 and other bacterial PIF1 helicases may act as accessory helicases at replication forks to sense ssDNA levels behind the replicative helicase. Further, our findings predict that the domains of unknown function found in TePif1 homologs like S. cerevisiae Pif1 and Rrm3 may contain motifs needed for ssDNA binding.
The College of Arts