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Transcriptional proofreading in Escherichia coli
R T Libby1, J L Nelson, J M Calvo
1University of Washington, Department of Genetics, Seattle 98195.
The EMBO Journal
|October 1, 1989
Summary
This study reveals a novel transcriptional proofreading mechanism in Escherichia coli RNA polymerase. This mechanism, involving NTPase activity, corrects errors during RNA synthesis, impacting transcription speed.
Area of Science:
- Molecular Biology
- Biochemistry
- Genetics
Background:
- RNA polymerase is crucial for gene transcription.
- Transcriptional fidelity is maintained through various mechanisms.
- The beta-subunit of RNA polymerase plays a role in transcription accuracy.
Purpose of the Study:
- To investigate a novel transcriptional proofreading mechanism.
- To characterize the NTPase activity of wild-type and mutant RNA polymerase.
- To understand the role of this mechanism in regulating transcription speed.
Main Methods:
- Purification of wild-type and mutant RNA polymerase holoenzyme from Escherichia coli.
- In vitro transcription assays using synthetic templates.
- Measurement of NTPase activity and its dependence on template and initiation complex integrity.
- Comparison of transcription and translation rates between wild-type and mutant strains.
Main Results:
- Wild-type RNA polymerase exhibits template-dependent NTPase activity, hydrolyzing noncognate NTPs.
- Mutant RNA polymerase, with increased transcriptional errors, lacks this NTPase activity.
- The NTPase activity is dependent on initiation complex integrity and transcriptional elongation.
- Transcription and translation of the lacZ gene were 17% faster in the mutant.
Conclusions:
- A novel transcriptional proofreading mechanism involving NTP hydrolysis exists in Escherichia coli.
- This mechanism, associated with the beta-subunit, limits transcription rate by removing noncognate NTPs.
- The findings suggest a direct link between proofreading and transcriptional efficiency.