Related Experiment Videos
The TRTGn motif stabilizes the transcription initiation open complex
Martin I Voskuil1, Glenn H Chambliss
1Department of Bacteriology, University of Wisconsin-Madison, 1550 Linden Drive, E. B. Fred Hall, 53706, Madison, WI, USA
Journal of Molecular Biology
|September 13, 2002
Summary
The extended -10 motif (TRTG) in bacterial promoters significantly stabilizes transcription initiation complexes. Mutations in this motif shorten the open complex half-life, impacting DNA strand separation during RNA polymerase activity.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- The extended -10 motif (5'-TRTG(n)-3') is crucial in many bacterial promoters, particularly in Gram-positive bacteria.
- This motif, also known as the -16 region, is frequently observed in promoters from Escherichia coli.
- Understanding its role is key to deciphering bacterial gene regulation.
Purpose of the Study:
- To investigate the functional impact of the extended -10 motif on transcription initiation.
- To analyze the role of this motif in promoter activity and open complex stability.
- To elucidate the mechanism by which the extended -10 motif influences DNA-strand separation.
Main Methods:
- Site-directed mutagenesis was employed to create base substitutions in the alpha-amylase promoter (amyP).
- Mutations were introduced to eliminate the influence of a competing promoter site (amyP2).
- Analysis of open complex formation, stability, and DNA melting dynamics was performed.
Main Results:
- Mutations in the TRTG motif of amyP destabilized the open complex, reducing its half-life up to 26-fold.
- The extended -10 motif was found to dramatically stabilize the open complex intermediate during transcription initiation.
- While the melted DNA region size remained similar, the TRTG motif mutant showed contraction upon nucleotide addition, indicating a role in maintaining strand separation.
Conclusions:
- The extended -10 (TRTG) motif is essential for stabilizing the open complex during transcription initiation.
- This motif plays a critical role in maintaining DNA-strand separation, particularly after the initial binding of RNA polymerase and nucleotides.
- The findings provide insights into the regulatory mechanisms of bacterial transcription.