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Escherichia coli YmdB regulates biofilm formation independently of its role as an RNase III modulator.

ABSTRACT: BACKGROUND: Ribonuclease III (RNase III) activity modulates hundreds of genes in Escherichia coli (E. coli). YmdB, a member of the macrodomain protein family, is one of known trans-acting regulators of RNase III activity; however, the significance of its regulatory role in specific bacterial cellular processes and related genes has not been determined. YmdB overexpression was used to model YmdB-induced RNase III inhibition in vivo, and microarray analysis identified gene targets and cellular processes related to RNase III inhibition. RESULTS: The expression of >2,000 E. coli genes was modulated by YmdB induction; 129 genes were strongly regulated, of which 80 have not been reported as RNase III targets. Of these, ten are involved in biofilm formation. Significantly, YmdB overexpression also inhibited biofilm formation via a process that is not uniquely dependent upon RNase III inhibition. Moreover, biofilm formation is interdependently regulated by RpoS, a known stress response regulator and biofilm inhibitor, and by YmdB. CONCLUSIONS: This is the first global profile of target genes modulated by YmdB-induced RNase III inhibition in E. coli, and the data reveal a novel, hitherto unrecognized regulatory role for YmdB in biofilm modulation.

SUBMITTER: Kim T

PROVIDER: S-EPMC4222554 | biostudies-literature | 2013

REPOSITORIES: biostudies-literature

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Escherichia coli YmdB regulates biofilm formation independently of its role as an RNase III modulator.

Kim Taeyeon T Lee Juyeon J Kim Kwang-sun KS

BMC microbiology 20131124

<h4>Background</h4>Ribonuclease III (RNase III) activity modulates hundreds of genes in Escherichia coli (E. coli). YmdB, a member of the macrodomain protein family, is one of known trans-acting regulators of RNase III activity; however, the significance of its regulatory role in specific bacterial cellular processes and related genes has not been determined. YmdB overexpression was used to model YmdB-induced RNase III inhibition in vivo, and microarray analysis identified gene targets and cellu ...[more]

PMID: 24267348

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Project description:UnlabelledThe complex posttranscriptional regulation mechanism of the Escherichia coli pnp gene, which encodes the phosphorolytic exoribonuclease polynucleotide phosphorylase (PNPase), involves two endoribonucleases, namely, RNase III and RNase E, and PNPase itself, which thus autoregulates its own expression. The models proposed for pnp autoregulation posit that the target of PNPase is a mature pnp mRNA previously processed at its 5' end by RNase III, rather than the primary pnp transcript (RNase III-dependent models), and that PNPase activity eventually leads to pnp mRNA degradation by RNase E. However, some published data suggest that pnp expression may also be regulated through a PNPase-dependent, RNase III-independent mechanism. To address this issue, we constructed isogenic Δpnp rnc(+) and Δpnp Δrnc strains with a chromosomal pnp-lacZ translational fusion and measured β-galactosidase activity in the absence and presence of PNPase expressed by a plasmid. Our results show that PNPase also regulates its own expression via a reversible RNase III-independent pathway acting upstream from the RNase III-dependent branch. This pathway requires the PNPase RNA binding domains KH and S1 but not its phosphorolytic activity. We suggest that the RNase III-independent autoregulation of PNPase occurs at the level of translational repression, possibly by competition for pnp primary transcript between PNPase and the ribosomal protein S1.ImportanceIn Escherichia coli, polynucleotide phosphorylase (PNPase, encoded by pnp) posttranscriptionally regulates its own expression. The two models proposed so far posit a two-step mechanism in which RNase III, by cutting the leader region of the pnp primary transcript, creates the substrate for PNPase regulatory activity, eventually leading to pnp mRNA degradation by RNase E. In this work, we provide evidence supporting an additional pathway for PNPase autogenous regulation in which PNPase acts as a translational repressor independently of RNase III cleavage. Our data make a new contribution to the understanding of the regulatory mechanism of pnp mRNA, a process long since considered a paradigmatic example of posttranscriptional regulation at the level of mRNA stability.

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Escherichia coli YmdB regulates biofilm formation independently of its role as an RNase III modulator.

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Escherichia coli YmdB regulates biofilm formation independently of its role as an RNase III modulator.

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