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Synergies between RNA degradation and trans-translation in... » Isaúde
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BMC microbiology [electronic resource]
2012-11-21 02:07:12

Synergies between RNA degradation and trans-translation in Streptococcus pneumoniae: cross regulation and co-transcription of RNase R and SmpB

Descrição: Background:Ribonuclease R (RNase R) is an exoribonuclease that recognizes and degrades a wide range of RNA molecules. It is a stress-induced protein shown to be important for the establishment of virulence in several pathogenic bacteria. RNase R has also been implicated in the trans-translation process. Transfer-messenger RNA (tmRNA/SsrA RNA) and SmpB are the main effectors of trans-translation, an RNA and protein quality control system that resolves challenges associated with stalled ribosomes on non-stop mRNAs. Trans-translation has also been associated with deficiencies in stress-response mechanisms and pathogenicity.Results:In this work we study the expression of RNase R in the human pathogen Streptococcus pneumoniae and analyse the interplay of this enzyme with the main components of the trans-translation machinery (SmpB and tmRNA/SsrA). We show that RNase R is induced after a 37[degree sign]C to 15[degree sign]C temperature downshift and that its levels are dependent on SmpB. On the other hand, our results revealed a strong accumulation of the smpB transcript in the absence of RNase R at 15[degree sign]C. Transcriptional analysis of the S. pneumoniae rnr gene demonstrated that it is co-transcribed with the flanking genes, secG and smpB. Transcription of these genes is driven from a promoter upstream of secG and the transcript is processed to yield mature independent mRNAs. This genetic organization seems to be a common feature of Gram positive bacteria, and the biological significance of this gene cluster is further discussed.Conclusions:This study unravels an additional contribution of RNase R to the trans-translation system by demonstrating that smpB is regulated by this exoribonuclease. RNase R in turn, is shown to be under the control of SmpB. These proteins are therefore mutually dependent and cross-regulated. The data presented here shed light on the interactions between RNase R, trans-translation and cold-shock response in an important human pathogen.

Identificador: doi:10.1186/1471-2180-12-268
Volume: 0
Página: 2 a


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