Submitted to: Journal of Bacteriology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/30/2006
Publication Date: 6/4/2006
Citation: Roberts, C., Anderson, K.L., Murphy, E., Projan, S.J., Mounts, W., Hurlburt, B.K., Smeltzer, M., Overbeek, R., Disz, T., Dunman, P.M. 2006. Characterizing the effect of the staphylococcus aureus virulence factor regulator, sara, on log-phase mrna half-lives. Journal of Bacteriology. 188(7):2593-2603. Interpretive Summary: Staphylococcus aureus is a potent human pathogen and cause of food-poisoning agent. SarA, which was previously shown to be a DNA-binding, regulatory protein, is shown in this paper to also regulate messenger RNA (mRNA) stability. Using a combination of GeneChip, real-time polymerase chain reaction (RT-PCR) and blotting techniques, the half-lives of all mRNAs in wild type and SarA mutant cells were determined. A significant number of mRNAs had shorter half-lives in the mutant. A few mRNAs were more stable. This work is significant because it reveals a new role for regulation by SarA.
Technical Abstract: Bacterial pathogens regulate virulence factor expression at both the level of transcription initiation and mRNA processing/turnover. Within Staphylococcus aureus, virulence factor transcript synthesis is regulated by a number of two-component regulatory systems, the DNA binding protein, SarA, and the SarA-family of homologues. However, little is known about the factors that modulate mRNA stability or influence transcript degradation within the organism. As our entry to characterizing these processes, S. aureus GeneChips were used to simultaneously determine the mRNA half-lives of all transcripts produced during log-phase growth. It was found that the majority of logphase transcripts (90%) have a short half-life (< 5 min), whereas, others are more stable, suggesting that cis- and/or trans-acting factors influence S. aureus mRNA stability. In support of this, it was found that two virulence factor transcripts, cna and spa, were stabilized in a sarA-dependent manner. These results were validated by complementation and Real Time PCR, and suggest that SarA may regulate target gene expression in a previously unrecognized manner by post-transcriptionally modulating mRNA turnover. Additionally, it was found that S. aureus produces a set of stable RNA molecules with no predicted open-reading frame. Based on the importance of the S. aureus agr RNA molecule, RNAIII, and small stable RNA molecules within other pathogens, it is possible that these RNA molecules influence biological processes within the organism.