Intrinsic transcript cleavage activity of RNA polymerase

Area of Science:

• Molecular Biology
• Biochemistry
• Genetics

Background:

• The GreA and GreB proteins in Escherichia coli are known transcript cleavage factors.
• These factors are believed to suppress transcription elongation arrest and potentially play a proofreading role.
• The precise enzymatic activities of RNA polymerase and the role of Gre factors require further elucidation.

Purpose of the Study:

• To investigate the intrinsic transcript cleavage activity of RNA polymerase.
• To determine the role of GreA and GreB proteins in transcript cleavage and elongation arrest.
• To understand the mechanism by which transcript cleavage antagonizes elongation arrest.

Main Methods:

• Utilizing an Escherichia coli greA-greB- mutant strain.
• Analyzing RNA polymerase activity in ternary complexes.
• Investigating the effect of mildly alkaline pH on transcript cleavage and elongation.

Main Results:

• Escherichia coli RNA polymerase exhibits significant intrinsic transcript cleavage activity.
• Mildly alkaline pH mimics the function of Gre proteins by inducing transcript cleavage.
• Transcript cleavage antagonizes elongation arrest via a cleavage-and-restart mechanism.

Conclusions:

• Transcript cleavage is an intrinsic enzymatic activity of RNA polymerase, alongside polymerization and pyrophosphorolysis.
• GreA and GreB proteins enhance, rather than solely provide, the transcript cleavage activity.
• RNA polymerase possesses a self-correcting mechanism involving transcript cleavage to overcome elongation blocks.