PcrA Helicase Removes Trafficking Barriers.

PcrA interacts with the RNA polymerase and might contribute to mitigate replication-transcription conflicts (RTCs). We show that PcrA depletion lethality is partially suppressed by inactivation, but cell viability is significantly reduced by or inactivation. Following PcrA depletion, cells lacking RnhC or DinG are extremely sensitive to DNA damage. Chromosome segregation is not further impaired by or inactivation but is blocked by or inactivation upon PcrA depletion. Despite our efforts, we could not construct a Δ Δ strain. These observations support the idea that PcrA dismantles RTCs. Purified PcrA, which binds single-stranded (ss) DNA over RNA, is a ssDNA-dependent ATPase and preferentially unwinds DNA in a 3'→5'direction. PcrA unwinds a 3'-tailed RNA of an RNA-DNA hybrid significantly faster than that of a DNA substrate. Our results suggest that a replicative stress, caused by mis-incorporated rNMPs, indirectly increases cell viability upon PcrA depletion. We propose that PcrA, in concert with RnhC or DinG, contributes to removing spontaneous or enzyme-driven R-loops, to counteract deleterious trafficking conflicts and preserve to genomic integrity.