Polynucleotide phosphorylase, RNase II and RNase E play different roles in the in vivo modulation of polyadenylation in Escherichia coli
Article first published online: 18 JAN 2002
Volume 36, Issue 4, pages 982–994, May 2000
How to Cite
Mohanty, B. K. and Kushner, S. R. (2000), Polynucleotide phosphorylase, RNase II and RNase E play different roles in the in vivo modulation of polyadenylation in Escherichia coli. Molecular Microbiology, 36: 982–994. doi: 10.1046/j.1365-2958.2000.01921.x
- Issue published online: 18 JAN 2002
- Article first published online: 18 JAN 2002
- Received 10 January, 2000; revised 8 March, 2000; accepted 13 March, 2000.
Poly(A) tails in Escherichia coli are hypothesized to provide unstructured single-stranded substrates that facilitate the degradation of mRNAs by ribonucleases. Here, we have investigated the role that such nucleases play in modulating polyadenylation in vivo by measuring total poly(A) levels, polyadenylation of specific transcripts, growth rates and cell viabilities in strains containing various amounts of poly(A) polymerase I (PAP I), polynucleotide phosphorylase (PNPase), RNase II and RNase E. The results demonstrate that both PNPase and RNase II are directly involved in regulating total in vivo poly(A) levels. RNase II is primarily responsible for degrading poly(A) tails associated with 23S rRNA, whereas PNPase is more effective in modulating the polyadenylation of the lpp and 16S rRNA transcripts. In contrast, RNase E appears to affect poly(A) levels indirectly through the generation of new 3′ termini that serve as substrates for PAP I. In addition, whereas excess PNPase suppresses polyadenylation by more than 70%, the toxicity associated with increased poly(A) levels is not reduced. Conversely, toxicity is significantly reduced in the presence of excess RNase II. Overproduction of RNase E leads to increased polyadenylation and no reduction in toxicity.