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Polyadenylation of mRNA in prokaryotes
1Boston Biomedical Research Institute, Massachusetts 02114, USA. sarkar@bbri.harvard.edu
Abstract:
The 3'-ends of both prokaryotic and eukaryotic mRNA are polyadenylated, but the poly(A) tracts of prokaryotic mRNA are generally shorter, ranging from 15 to 60 adenylate residues and associated with only 2-60% of the molecules of a given mRNA species. The sites of polyadenylation of bacterial mRNA are diverse and include the 3'-ends of primary transcripts, the sites of endonucleolytic processing in the 3' untranslated and intercistronic regions, and sites within the coding regions of mRNA degradation products. The diversity of polyadenylation sites suggests that mRNA polyadenylation in prokaryotes is a relatively indiscriminate process that can occur at all mRNA's 3'-ends and does not require specific consensus sequences as in eukaryotes. Two poly(A) polymerases have been identified in Escherichia coli. They are encoded by unlinked genes, neither of which is essential for growth, suggesting significant functional overlap. Polyadenylation promotes the degradation of a regulatory RNA that inhibits the replication of bacterial plasmids and may play a similar role in the degradation of mRNA. However, under certain conditions, poly(A) tracts may lead to mRNA stabilization. Their ability to bind S1 ribosomal protein suggests that poly(A) tracts may also play a role in mRNA translation.
Insights
Prokaryotic mRNA polyadenylation is a diverse process, differing from eukaryotes. Poly(A) tracts in bacteria can influence mRNA degradation and translation, with two non-essential poly(A) polymerases identified in Escherichia coli.
Area of Science:
- Molecular Biology
- Microbiology
- Genetics
Background:
- Both prokaryotic and eukaryotic messenger RNA (mRNA) undergo polyadenylation at their 3'-ends.
- Prokaryotic mRNA poly(A) tracts are typically shorter (15-60 adenylate residues) and less frequently associated with mRNA molecules compared to eukaryotes.
Purpose of the Study:
- To investigate the characteristics and functions of mRNA polyadenylation in prokaryotes, specifically in Escherichia coli.
- To explore the diversity of polyadenylation sites and the enzymes involved in bacterial mRNA processing.
Main Methods:
- Analysis of polyadenylation sites in bacterial mRNA.
- Identification and characterization of poly(A) polymerases in Escherichia coli.
- Investigation of the role of poly(A) tracts in mRNA degradation and translation.
Main Results:
- Bacterial mRNA polyadenylation occurs at diverse sites, including transcript ends, processing sites, and within coding regions, suggesting an indiscriminate process.
- Two distinct poly(A) polymerases were identified in E. coli, encoded by non-essential genes.
- Polyadenylation can promote mRNA degradation but may also stabilize mRNA under certain conditions and potentially influence translation via S1 ribosomal protein binding.
Conclusions:
- Prokaryotic mRNA polyadenylation is a flexible process not requiring specific eukaryotic-like consensus sequences.
- The identified poly(A) polymerases in E. coli likely have overlapping functions.
- Poly(A) tracts in bacteria play multifaceted roles in gene expression, affecting mRNA stability and translation.