Molecular and Cellular Biology, June 2000, p. 4169-4180, Vol. 20, No. 11
Department of Molecular Genetics,
Biochemistry and Microbiology, University of Cincinnati, Cincinnati,
Ohio
Received 21 January 2000/Returned for modification 19 February
2000/Accepted 28 February 2000
Aberrant expression of developmentally silenced genes,
characteristic of tumor cells and regenerating tissue, is highly
correlated with increased cell proliferation. By modeling this process
in vitro in synthetic nuclei, we find that DNA replication leads to
deregulation of established developmental expression patterns. Chromatin assembly in the presence of adult mouse liver nuclear extract
mediates developmental stage-specific silencing of the tumor marker
gene alpha-fetoprotein (AFP). Replication of silenced AFP chromatin in
synthetic nuclei depletes sequence-specific transcription repressors,
thereby disrupting developmentally regulated repression. Hepatoma-derived factors can target partial derepression of AFP, but
full transcription activation requires DNA replication. Thus, unscheduled entry into S phase directly mediates activation of a
developmentally silenced gene by (i) depleting developmental stage-specific transcription repressors and (ii) facilitating binding
of transactivators.
0270-7306/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
S-Phase Progression Mediates Activation of a
Silenced Gene in Synthetic Nuclei
*
Corresponding author. Mailing address: Dept. of
Molecular Genetics, Biochemistry and Microbiology, University of
Cincinnati, Cincinnati, OH 45267-0524. Phone: (513) 558-5541. Fax:
(513) 558-8474. E-mail: Michelle.Barton{at}UC.edu.
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