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Polyadenylylation destabilizes the rpsO mRNA of Escherichia coli
E Hajnsdorf1, F Braun, J Haugel-Nielsen
1Institut de Biologie Physico-Chimique, Paris, France.
Abstract:
The rpsO mRNA, encoding ribosomal protein S15, is only partly stabilized when the three ribonucleases implicated in its degradation--RNase E, polynucleotide phosphorylase, and RNase II--are inactivated. In the strain deficient for RNase E and 3'-to-5' exoribonucleases, degradation of this mRNA is correlated with the appearance of posttranscriptionally elongated molecules. We report that these elongated mRNAs harbor poly(A) tails, most of which are fused downstream of the 3'-terminal hairpin at the site where transcription terminates. Poly(A) tails are shorter in strains containing 3'-to-5' exoribonucleases. Inactivation of poly(A) polymerase I (pcnB) prevents polyadenylylation and stabilizes the rpsO mRNA if RNase E is inactive. In contrast polyadenylylation does not significantly modify the stability of rpsO mRNA undergoing RNase E-mediated degradation.
Insights
Polyadenylation, the addition of poly(A) tails to mRNA, impacts ribosomal protein S15 (rpsO) mRNA stability. Preventing polyadenylation stabilizes rpsO mRNA when specific ribonucleases are inactive.
Area of Science:
- Molecular Biology
- RNA Metabolism
- Gene Expression Regulation
Background:
- Ribonucleases (RNases) like RNase E, polynucleotide phosphorylase (PNPase), and RNase II are key enzymes in mRNA degradation.
- The stability of ribosomal protein S15 (rpsO) mRNA is incompletely understood, particularly its regulation beyond major RNase activity.
Purpose of the Study:
- To investigate the role of polyadenylation in the degradation and stability of rpsO mRNA.
- To elucidate the relationship between polyadenylation, transcription termination, and the activity of specific ribonucleases.
Main Methods:
- Analysis of rpsO mRNA degradation in bacterial strains with specific RNase deficiencies.
- Identification and characterization of posttranscriptionally modified mRNA species, including polyadenylated and elongated forms.
- Genetic inactivation of poly(A) polymerase I (pcnB) to assess the impact on mRNA stability.
Main Results:
- Inactivation of RNase E and 3'-to-5' exoribonucleases leads to the accumulation of polyadenylated and elongated rpsO mRNA molecules.
- Poly(A) tail length is inversely correlated with the presence of 3'-to-5' exoribonucleases.
- Disruption of polyadenylation via pcnB inactivation stabilizes rpsO mRNA when RNase E is also inactive.
Conclusions:
- Polyadenylation by poly(A) polymerase I (pcnB) is a significant factor in the degradation of rpsO mRNA, especially under conditions of limited RNase activity.
- The 3'-terminal hairpin influences the site of polyadenylation and subsequent mRNA processing.
- Polyadenylation's impact on mRNA stability is context-dependent, varying with the specific RNase machinery involved.