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Mol Cell Biol, April 1998, p. 2406-2415, Vol. 18, No. 4
Department of Molecular Biology and Genetics,
The Johns Hopkins University School of Medicine, Baltimore,
Maryland 21205,1 and
Department of
Biological Sciences, SUNY Buffalo, Buffalo, New York
142602
Received 15 September 1997/Returned for modification 20 November
1997/Accepted 23 January 1998
Yeast two-hybrid screening has led to the identification of a
family of proteins that interact with the repetitive C-terminal repeat
domain (CTD) of RNA polymerase II (A. Yuryev et al., Proc. Natl. Acad.
Sci. USA 93:6975-6980, 1996). In addition to serine/arginine-rich SR
motifs, the SCAFs (SR-like CTD-associated factors) contain discrete
CTD-interacting domains. In this paper, we show that the
CTD-interacting domain of SCAF8 specifically binds CTD molecules phosphorylated on serines 2 and 5 of the consensus sequence
Tyr1Ser2Pro3Thr4Ser5Pro6Ser7. In addition, we demonstrate that SCAF8 associates with
hyperphosphorylated but not with hypophosphorylated RNA polymerase II
in vitro and in vivo. This result suggests that SCAF8 is not present in
preinitiation complexes but rather associates with elongating RNA
polymerase II. Immunolocalization studies show that SCAF8 is present in
granular nuclear foci which correspond to sites of active
transcription. We also provide evidence that SCAF8 foci are associated
with the nuclear matrix. A fraction of these sites overlap with a
subset of larger nuclear speckles containing phosphorylated polymerase II. Taken together, our results indicate a possible role for SCAF8 in
linking transcription and pre-mRNA processing.
0270-7306/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
A Nuclear Matrix Protein Interacts with the
Phosphorylated C-Terminal Domain of RNA Polymerase II
*
Corresponding author. Mailing address: Department of
Molecular Biology and Genetics, The Johns Hopkins University School of Medicine, 725 N. Wolfe St., Baltimore, MD 21205-2185. Phone: (410) 955-4719. Fax: (410) 502-6718. E-mail:
jeff_corden{at}qmail.bs.jhu.edu.
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