Regulation of plasmid R1 replication: PcnB and RNase E expedite the decay of the antisense RNA, CopA

Abstract

SummaryThe replication frequency of plasmid R1 is controlled by an unstable antisense RNA, CopA, which, by binding to its complementary target, blocks translation of the replication rate-limiting protein RepA. Since the degree of inhibition is directly correlated with the intracellular concentration of CopA, factors affecting CopA turnover can also alter plasmid copy number. We show here that PcnB (PAP I -a poly(A)polymerase of Escherichia coli ) is such a factor. Previous studies have shown that the copy number of ColE1 is decreased in pcnB mutant strains because the stability of the RNase E processed form of RNAI, the antisense RNA regulator of ColE1 replication, is increased. We find that, analogously, the twofold reduction in R1 copy number caused by a pcnB lesion is associated with a corresponding increase in the stability of the RNase E-generated 3Ј cleavage product of CopA. These results suggest that CopA decay is initiated by RNase E cleavage and that PcnB is involved in the subsequent rapid decay of the 3Ј CopA stem-loop segment. We also find that, as predicted, under conditions in which CopA synthesis is unaffected, pcnB mutation reduces RepA translation and increases CopA stability to the same extent.

Bacterial plasmids replication of extrachromosomal genetic elements encoding resistance to antimicrobial compounds

“…CopA controls initiation of R1 replication by interacting with CopT resulting in posttranscriptional inhibition of RepA synthesis (192)(193)(194)(195)(196)(197)(198)(199)(200). The concentration of CopA in the cytosol is influenced by the PcnB and RNase E proteins (201). On the other hand, in the case of ColE1-type plasmids the antisense RNA acts by interacting with the RNA primer.…”

Noncoding RNA control of the making and breaking of sugars

“…Polyadenylation-dependent destabilization had for long been known to affect cis-encoded antisense RNAs of bacterial plasmids (Xu et al 1993;Dam Mikkelsen and Gerdes 1997;Söderbom et al 1997), yet GlmY was the first chromosomal sRNA whose polyadenylation impacts on the synthesis of a cellular protein.…”

Regulating the regulators: How ribonucleases dictate the rules in the control of small non-coding RNAs

“…Subsequent exonucleolytic degradation by either PNPase or RNase II 133 is particularly dependent on PAPI, since the 3' CopA decay fragment is stabilized in a pcnB strain. 134 However, the pcnB dependence of RNAI and CopA degradation is different: RNAI was stabilized more than 10-fold in a pcnB mutant strain, 131,132 whereas only a two-fold stabilization effect was seen for CopA. 134 There is no clear justification for this difference, although it is most likely due to differences in the structure of the sRNAs or to the involvement of additional enzymes.…”