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Updated: Jul 18, 2026
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In vivo Application of the REMOTE-control System for the Manipulation of Endogenous Gene Expression
Published on: March 29, 2019
lac repressor acts by modifying the initial transcribing complex so that it cannot leave the promoter.
1Department of Microbiology, College of Physicians and Surgeons, Columbia University, New York, New York 10032.
Cell
|August 23, 1991
Summary
The lac repressor protein prevents RNA polymerase from elongating transcripts at the lac UV5 promoter by augmenting a natural pause site. This mechanism blocks promoter escape and generates short, abortive RNA molecules.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- The lac repressor protein regulates gene expression by binding to the lac operator.
- RNA polymerase initiates transcription at promoter regions, but promoter escape is a critical step.
- Abortive transcription occurs when RNA polymerase releases short RNA fragments without elongating the transcript.
Purpose of the Study:
- To investigate the mechanism by which the lac repressor inhibits RNA polymerase activity at the lac UV5 promoter.
- To determine if the repressor's action involves augmenting intrinsic promoter pause sites.
- To explore the implications of this mechanism for promoter clearance and abortive transcription.
Main Methods:
- Formation of a joint complex between RNA polymerase and the lac repressor at the lac UV5 promoter.
- Analysis of RNA synthesis, focusing on abortive oligomer generation and transcript length.
- Investigating the effect of substrate concentration on transcription.
- Utilizing a specific RNA polymerase mutation that mimics the repressor's effect.
Main Results:
- The joint complex between RNA polymerase and lac repressor is blocked from promoter escape, producing abortive RNA oligomers.
- Transcription is highly sensitive to substrate concentration, indicating a pause site.
- The repressor augments a natural high nucleotide concentration (kNTP) pause site within the promoter.
- A specific RNA polymerase mutation phenocopies the repressor's effect, blocking promoter clearance and shortening abortive products.
Conclusions:
- The lac repressor inhibits transcription elongation by enhancing a promoter-intrinsic pause site, thereby preventing promoter escape.
- This mechanism of augmenting pause sites is likely a widespread strategy for regulating transcription initiation.
- Understanding these regulatory mechanisms is crucial for comprehending gene expression control.
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