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Proc Natl Acad Sci U S A. 1993 Feb 1;90(3):843-7.

Identification of a 3'-->5' exonuclease activity associated with human RNA polymerase II.

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Department of Biology, University of Oregon, Eugene 97403.


Human RNA polymerase II is shown to be associated with a 3'-->5' exonuclease activity that removes nucleoside 5'-monophosphates from the 3' end of the transcripts in isolated ternary complexes. This activity is stimulated by SII, a protein that acts as a transcription elongation factor in vitro. In addition, we show that another transcription factor, TFIIF, stimulates a competing pyrophosphorolysis reaction. These findings raise interesting questions about the roles of these activities in vivo, including the possibility that this RNA polymerase may proofread the nascent transcript.

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