RNase HIII Is Important for Okazaki Fragment Processing in Bacillus subtilis

All cells are required to resolve the different types of RNA-DNA hybrids that formin vivo . When RNA-DNA hybrids persist, cells experience an increase in mutation rate and problems with DNA replication. Okazaki fragment synthesis on the lagging strand requires an RNA primer to begin synthesis of each fragment. The mechanism of RNA removal from Okazaki fragments remains unknown in bacteria that lack RNase HI. We examined Okazaki fragment processingin vitro and found that RNase HIII in conjunction with DNA polymerase I represent the most efficient repair pathway. We also assessed the contribution of YpcP and found that YpcP is a 5′ to 3′ exonuclease that prefers RNA substrates with activity on Okazaki and flap substratesin vitro .