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Proc Natl Acad Sci U S A. 1994 Dec 20;91(26):12691-5.

Phosphorylation negatively regulates the function of coactivator PC4.

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1
Laboratory of Biochemistry and Molecular Biology, Rockefeller University, New York, NY 10021.

Abstract

Human positive cofactor 4 (PC4) mediates activator-dependent transcription by RNA polymerase II, apparently through interactions with transcriptional activators and the basal transcription machinery. We report here that PC4 function is modulated by in vivo phosphorylation. Protein-protein interaction studies and in vitro transcription assays demonstrate that only the nonphosphorylated form of PC4 is functionally active. Although recombinant PC4 can be phosphorylated by casein kinase II and protein kinase C in vitro, mutational and mass spectrometric analyses suggest that the in vivo hyperphosphorylation of PC4 is mediated mainly by casein kinase II and restricted to an N-terminal serine-rich region. These observations provide one example of a transcriptional cofactor that is negatively regulated by casein kinase II phosphorylation.

PMID:
7809103
PMCID:
PMC45505
[Indexed for MEDLINE]
Free PMC Article
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