RNase HIII Is Important for Okazaki Fragment Processing in Bacillus subtilis

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Persistent RNA-DNA hybrids cause replication stress, DNA breaks, and neurological issues.
• Okazaki fragment synthesis necessitates RNA primers, creating RNA-DNA strands during replication.
• RNA removal mechanisms for Okazaki fragments in bacteria lacking RNase HI are unknown.

Purpose of the Study:

• To investigate the mechanism of Okazaki fragment maturation in bacteria lacking RNase HI.
• To identify enzymes involved in RNA primer removal from Okazaki fragments.
• To elucidate the roles of RNase HII, HIII, YpcP, and DNA polymerase I in this process.

Main Methods:

• Reconstitution of Okazaki fragment repair in vitro using purified recombinant enzymes from Bacillus subtilis.
• Enzymatic assays to assess incision, degradation, and polymerization activities.
• Characterization of substrate specificity for nucleases and polymerases involved.

Main Results:

• RNase HII and HIII can incise Okazaki fragments, with mild stimulation by single-stranded DNA binding protein (SSB).
• RNase HIII and DNA polymerase I form the primary pathway for Okazaki fragment maturation in vitro.
• YpcP acts as a 5' to 3' nuclease with a preference for degrading RNA in Okazaki fragments and flap substrates.

Conclusions:

• RNase HIII and DNA polymerase I are crucial for efficient Okazaki fragment maturation.
• YpcP contributes to RNA removal from Okazaki fragments, complementing the primary pathway.
• Understanding these mechanisms is vital for resolving RNA-DNA hybrids and preventing DNA replication problems.