Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.26.9 (ribonuclease)
 6,589 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Highly purified yeast RNA polymerase III ternary complexes were found to possess a hydrolytic chain retracting activity that cleaves nascent RNA from its 3'-OH end. Most of the shortened transcripts were capable of resuming RNA chain elongation, indicating that they remain stably associated with the enzyme-DNA complex. Analysis of the products of cleavage indicated that retraction primarily occurred in dinucleotide increments, but that mononucleotides were also excised at lower frequency. The ribonuclease activity was totally dependent on the presence of a divalent cation and was stimulated by the addition of non-cognate ribonucleotides. The inclusion of ATP in the reaction enhanced both the rate and extent of transcript cleavage. Evidence suggesting that the hydrolytic activity is intrinsic to RNA polymerase III and factor-independent is also presented. Transcript cleavage by RNA polymerase III ternary complexes appears to be more closely related to the intrinsic nucleolytic activity of vaccinia virus RNA polymerase ternary complexes than to TFIIS-dependent cleavage that has been described for RNA polymerase II ternary complexes.
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PMID:Hydrolytic cleavage of nascent RNA in RNA polymerase III ternary transcription complexes. 750 90

Fidelity of DNA and protein synthesis is regulated by a proofreading mechanism but function of a similar mechanism during RNA synthesis has not been demonstrated. Analysis of transcriptional fidelity and its control has been hampered by the necessity to employ complex DNA templates requiring either a promoter and initiation factors or 3'-extended templates. To circumvent this difficulty, we have created an RNA-DNA dumbbell template that can be recognized as a template-primer and extended by RNA polymerase II. By employing this system, we demonstrate that RNA polymerase II can misincorporate a nucleotide and carry out template-dependent elongation at the mispaired end. The transcripts containing misincorporated residues can be cleaved by the very slow 3'-->5' ribonuclease activity of the RNA polymerase II, but enhancement of this activity by the elongation factor TFIIS generates RNA with a high degree of fidelity. This enhanced preferential cleavage of misincorporated transcripts suggests an important role for TFIIS in maintaining transcriptional fidelity.
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PMID:Fidelity of RNA polymerase II transcription controlled by elongation factor TFIIS. 894 93