Autoregulation of greA Expression Relies on GraL Rather than on greA Promoter Region

摘要

GreA is a well-characterized transcriptional factor that acts primarily by rescuing stalled RNA polymerase complexes, but has also been shown to be the major transcriptional fidelity and proofreading factor, while it inhibits DNA break repair. Regulation of gene expression itself is still not well understood. So far, it has been shown that its expression is driven by two overlapping promoters and that leader encodes a small RNA (GraL) that is acting on mRNA. It has been also shown that GreA autoinhibits its own expression . Here, we decided to investigate the inner workings of this autoregulatory loop. Transcriptional fusions with reporter carrying different modifications (made both to the promoter and leader regions) were made to pinpoint the sequences responsible for this autoregulation, while GraL levels were also monitored. Our data indicate that GreA mediated regulation of its own gene expression is dependent on GraL acting (a rare example of dual-action sRNA), rather than on the promoter region. However, a yet unidentified, additional factor seems to participate in this regulation as well. Overall, the GreA/GraL regulatory loop seems to have unique but hard to classify properties.