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Development of an in vitro mRNA decay system for Escherichia coli: poly(A) polymerase I is necessary to trigger
1Department of Genetics, University of Georgia, Athens 30602-7223, USA.
Abstract:
Using a novel Escherichia coli in vitro decay system in which polysomes are the source of both enzymes and mRNA, we demonstrate a requirement for poly(A) polymerase I (PAP I) in mRNA turnover. The in vitro decay of two different mRNAs (trxA and lpp) is triggered by the addition of ATP only when polysomes are prepared from s strain carrying the wild-type gene for PAP I (pcnB+). The relative decay rates of these two messages are similar in vitro and in vivo. Poly(A) tails are formed on both mRNAs, but no poly(A) are detected on the 3' end of mature 23S rRNA. The size distribution of poly(A) tails generated in vitro, averaging 50 nt in length, is comparable to that previously reported in vivo. PAP I activity is associated exclusively with the polysomes. Exogenously added PAP I does not restore mRNA decay to PAP I-polysomes, suggesting that, in vivo, PAP I may be part of a multiprotein complex. The potential of this in vitro system for analyzing mRNA decay in E. coli is discussed.
Insights
Poly(A) polymerase I (PAP I) is essential for Escherichia coli mRNA decay. This study developed an in vitro system to show PAP I
Area of Science:
- Molecular Biology
- Microbiology
Background:
- Messenger RNA (mRNA) turnover is a critical regulatory process in bacteria.
- Polyadenylation, the addition of a poly(A) tail, is implicated in mRNA decay in various organisms.
Purpose of the Study:
- To investigate the role of poly(A) polymerase I (PAP I) in Escherichia coli mRNA decay using a novel in vitro system.
- To characterize the requirements for mRNA decay initiation in vitro.
Main Methods:
- Development of an in vitro decay system using Escherichia coli polysomes as the source of enzymes and mRNA.
- Analysis of mRNA decay rates and poly(A) tail formation in the presence and absence of functional PAP I.
- Comparison of in vitro decay kinetics with previously reported in vivo data.
Main Results:
- mRNA decay in vitro is dependent on the presence of wild-type poly(A) polymerase I (PAP I) and ATP.
- Poly(A) tails are synthesized on decaying mRNAs, with an average length of 50 nucleotides.
- PAP I activity is localized to polysomes, and exogenous PAP I cannot rescue decay in deficient polysomes.
Conclusions:
- Poly(A) polymerase I (PAP I) is a key enzyme required for mRNA turnover in Escherichia coli.
- The in vitro system provides a valuable tool for studying the mechanisms of bacterial mRNA decay.
- PAP I likely functions as part of a larger multiprotein complex in vivo.