1. Divergent Contributions of Conserved Active Site Residues to Transcription by Eukaryotic RNA Polymerases I and II
- Author
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David A. Schneider, Olga V. Viktorovskaya, Craig D. Kaplan, Krysta L. Engel, Sarah L. French, Paul J. Vandeventer, Ping Cui, Ann L. Beyer, and Emily M. Pavlovic
- Subjects
Models, Molecular ,Transcription, Genetic ,DNA polymerase ,viruses ,Molecular Sequence Data ,RNA polymerase II ,General Biochemistry, Genetics and Molecular Biology ,RNA polymerase III ,Article ,03 medical and health sciences ,0302 clinical medicine ,RNA Polymerase I ,Catalytic Domain ,Transcriptional regulation ,RNA polymerase I ,Humans ,Amino Acid Sequence ,lcsh:QH301-705.5 ,Polymerase ,Conserved Sequence ,030304 developmental biology ,Genetics ,0303 health sciences ,biology ,Processivity ,lcsh:Biology (General) ,biology.protein ,RNA Polymerase II ,Transcription factor II D ,030217 neurology & neurosurgery - Abstract
SummaryMultisubunit RNA polymerases (msRNAPs) exhibit high sequence and structural homology, especially within their active sites, which is generally thought to result in msRNAP functional conservation. However, we show that mutations in the trigger loop (TL) in the largest subunit of RNA polymerase I (Pol I) yield phenotypes unexpected from studies of Pol II. For example, a well-characterized gain-of-function mutation in Pol II results in loss of function in Pol I (Pol II: rpb1- E1103G; Pol I: rpa190-E1224G). Studies of chimeric Pol II enzymes hosting Pol I or Pol III TLs suggest that consequences of mutations that alter TL dynamics are dictated by the greater enzymatic context and not solely the TL sequence. Although the rpa190-E1224G mutation diminishes polymerase activity, when combined with mutations that perturb Pol I catalysis, it enhances polymerase function, similar to the analogous Pol II mutation. These results suggest that Pol I and Pol II have different rate-limiting steps.
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