Regulation of DNA replication and the replication initiator, DnaA, in Bacillus subtilis

Abstract

DNA replication is a highly regulated process across all organisms. Improper regulation of DNA replication can be detrimental. I identified an overinitiating, conditional synthetic lethal mutant of Bacillus subtilis. I isolated suppressors of this mutant and uncovered novel genes associated with DNA replication. These suppressors acted both at the steps of initiation and elongation to overcome the detrimental replication initiation of the synthetic lethal [delta]yabA dnaA 1 mutant. One class of suppressors decreased levels of the replicative helicase, DnaC. I showed that decreased levels of helicase are sufficient to limit replication initiation under fast growth conditions. I also explored the regulation of DnaA as a transcription factor. The replication initiation inhibitor, YabA, binds to DnaA and prevents its cooperative binding at the origin. In addition to its role in replication initiation, DnaA also directly regulates expression of several genes. YabA has been shown to inhibit DnaA binding at several promoters but its effect on DnaA-mediated gene expression is unclear. I found that YabA inhibits sda activation by DnaA but does not significantly affect repression of ywlC by DnaA. Lastly, I showed that YabA appears to stimulate autoregulation of dnaA. This preliminary data illustrates a role for YabA regulation in DnaA-mediated gene expression.