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Elongation factor-dependent transcript shortening by template-engaged RNA polymerase II.
1Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322.
The Journal of Biological Chemistry
|February 25, 1992
Summary
RNA polymerase II exhibits a novel RNA cleavage activity, removing nucleotides from nascent transcripts within elongation complexes. This process, dependent on metal ions and factor SII, may function as a proofreading mechanism.
Area of Science:
- Molecular Biology
- Enzymology
- Gene Expression
Background:
- DNA polymerases and bacterial RNA polymerases possess nucleotide removal activity.
- This exonuclease activity is crucial for DNA synthesis fidelity.
- RNA polymerase II's role in transcription elongation is well-established.
Purpose of the Study:
- To investigate a novel in vitro activity of RNA polymerase II.
- To characterize the cleavage of RNA chains within active elongation complexes.
- To determine the factors involved in this novel RNA cleavage activity.
Main Methods:
- Utilizing in vitro transcription assays with arrested elongation complexes.
- Analyzing nascent RNA cleavage after removal of free nucleotides.
- Assessing the dependence on divalent metal cations and transcription elongation factor SII.
Main Results:
- RNA polymerase II was observed to cleave RNA chains within active elongation complexes.
- Cleavage occurred at a transcriptional pause site in a human gene.
- The resulting 3'-end remained associated with the complex and was extendable.
- Cleavage was dependent on divalent metal cations and transcription elongation factor SII.
Conclusions:
- RNA polymerase II possesses a novel transcript cleavage activity.
- This activity may be linked to the function of transcription elongation factor SII.
- The cleavage activity could represent a proofreading mechanism for RNA polymerase II.