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Artificial RNA Polymerase II Elongation Complexes for Dissecting Co-transcriptional RNA Processing Events
Published on: May 13, 2019
The poly(A)-dependent transcriptional pause is mediated by CPSF acting on the body of the polymerase
Anita Nag1, Kazim Narsinh, Harold G Martinson
1Department of Chemistry and Biochemistry and the Molecular Biology Institute, University of California at Los Angeles, Los Angeles, California 90095-1569, USA.
Abstract:
Eukaryotic poly(A) signals direct mRNA 3'-end processing and also pausing and termination of transcription. We show that pausing and termination require the processing factor CPSF, which binds the AAUAAA hexamer of the mammalian poly(A) signal. Pausing does not require the RNA polymerase II C-terminal domain (CTD) or the cleavage stimulation factor, CstF, that binds the CTD. Pull-down experiments show that CPSF binds, principally through its 30-kDa subunit, to the body of the polymerase. CPSF can also bind CstF, but this seems to be mutually exclusive with polymerase binding. We suggest that CPSF, while binding the body of the polymerase, scans for hexamers in the extruding RNA. Any encounter with a hexamer triggers pausing. If the hexamer is part of a functional poly(A) signal, CstF is recruited and binds CPSF, causing it to release the polymerase body and move (with CstF) to the CTD.
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