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The polycistronic mRNA of the Zymomonas mobilis glf-zwf-edd-glk operon is subject to complex transcript processing
1School of Biological Sciences, University of Nebraska, Lincoln 68588-0118.
Abstract:
The full-length 6.14-kb polycistronic glf-zwf-edd-glk mRNA from Zymomonas mobilis appears to be processed by endonucleolytic cleavage, resulting in the formation of several discrete transcripts. Northern analysis and transcript mapping revealed that the processed transcripts correspond to functional mono-, di-, or tricistronic messages. The relative abundance of the gene-specific, functional messages was measured. Expression of zwf and edd correlated well with functional message levels. Disproportionally high levels of the glk-specific mRNAs might compensate for the instability of glucokinase by allowing increased translation. The relative abundance of the discrete transcripts was shown to be a function of their respective decay rates. Northern analysis of the fate of the 6.14-kb transcript after inhibition of transcription by rifampin showed that the abundance of shorter, more stable transcripts increased at the expense of longer, less stable transcripts. This is suggestive of endonucleolytic mRNA processing. The most abundant 5' and 3' transcript ends were found to lie within secondary structures that probably impart stability to the most abundant mRNAs.
Insights
Zymomonas mobilis mRNA undergoes endonucleolytic cleavage, producing stable, functional transcripts. This processing regulates gene expression by controlling transcript abundance and stability.
Area of Science:
- Microbial molecular biology
- Bacterial gene expression regulation
- RNA processing mechanisms
Background:
- Zymomonas mobilis possesses a 6.14-kb polycistronic mRNA encoding glf, zwf, edd, and glk.
- Understanding mRNA processing is crucial for deciphering gene regulation in bacteria.
Purpose of the Study:
- To investigate the processing of the polycistronic glf-zwf-edd-glk mRNA in Zymomonas mobilis.
- To determine the relationship between mRNA processing, transcript stability, and gene expression levels.
Main Methods:
- Northern blot analysis to detect and map mRNA transcripts.
- Transcript mapping to identify discrete mRNA species.
- Analysis of transcript decay rates using rifampin to inhibit transcription.
Main Results:
- The polycistronic mRNA is processed into discrete mono-, di-, and tricistronic functional messages.
- Transcript abundance correlates with gene-specific decay rates.
- Stable transcripts accumulate as less stable ones degrade, suggesting endonucleolytic processing.
- Abundant transcript ends are located within stable secondary structures.
Conclusions:
- Endonucleolytic cleavage is a key mechanism for processing polycistronic mRNA in Zymomonas mobilis.
- mRNA processing and stability significantly influence the regulation of gene expression.
- Secondary structures at transcript ends contribute to mRNA stability.