Genetic Investigations into the mRNA Polyadenylation Function of SprE

Abstract

<bold>Abstract</bold>

In <italic>Escherichia coli</italic>, the orphan response regulator SprE (RssB) post-transcriptionally regulates the alternate sigma factor, RpoS (&sigma;<super>S</super>). During exponential phase, SprE binds to RpoS and directs it to the ClpXP protease for degradation; however upon carbon starvation lowered ATP levels inhibit this process. Recently SprE was shown to have a second function regulating mRNA polyadenylation and stability. During stationary phase SprE is required to maintain the mRNA degradosome complex and change the intracellular localization of Poly A polymerase (PAP I). Deleting <italic>sprE</italic> decreases bulk polyadenylation and increases the stability of certain mRNAs suggesting that SprE stimulates degradation of at least a subset of transcripts in log phase. To gain insight into the nature of the transcripts affected by SprE we have employed microarrays and have determined that SprE affects about 100 genes whose products are involved in sugar and amino acid catabolism. Analysis of two such operons, <italic>tnaAB</italic> and <italic>glpTQ</italic> , has identified the 3&rsquo; Untranslated region (UTR) of these mRNAs is required for degradation due to SprE. The use of the 3&rsquo; UTR and the control of mRNA stability represents a novel form of post-transcriptional regulation in bacteria.