ANNE LERESCHE,1 VERONICA
J. WOLF,2 AND JOEL M.
GOTTESFELD
Department of Molecular Biology, The Scripps Research
Institute, 10550 N. Torrey Pines Road, La Jolla, California
92037
Abstract
Nuclear transcription is repressed when eukaryotic cells enter
mitosis. Using Xenopus egg extracts shifted to the mitotic
state with recombinant cyclin B1 protein, we have been able to
reproduce mitotic repression of transcription in vitro.
Active RNA polymerase III transcription is observed in interphase
extracts in the absence of added cyclin, but is strongly
repressed by the induction of cdc2/cyclin B (maturation/mitosis
promoting factor, MPF) kinase activity in the mitotic extract.
Studies with protein kinase inhibitors show that protein
phosphorylation is required for repression. Add-back experiments
indicate that repression of class III gene transcription is due
to inactivation of the transcription factor TFIIIB. TFIIIB is
composed of the TATA-box binding protein (TBP) and TBP-associated
factors of 75 and 92 kDa. In the present study, we show that TBP
and a polypeptide of 92 kDa are substrates of the mitotic kinase
in highly purified TFIIIB fractions. We also show that a
phosphatase present in the Xenopus egg extract can
reactivate transcription after repression by the mitotic kinases.
This result suggests a mechanism for reactivation of
transcription after exit from mitosis into the G1 phase of the
cell cycle. As for pol III genes, purified cdc2/cyclin B kinase
is sufficient to inhibit transcription by RNA polymerase II in a
reconstituted transcription system containing the basal
transcription factors and polymerase.
EXPERIMENTAL CELL RESEARCH 229
282 - 288 (1996)
ARTICLE NO. 0373
Copyright © 1996 Academic Press, Inc.
1Address (1996): Baxter
Pharmaceuticals, Nechatel, Switzerland.
2Address
(1996): Department of Structural Biology, University of Colorado
Health Sciences Center, Denver, CO 80206.
We are currently working on the web site. Please report errors or problems.
