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Molecular and Cellular Biology, January 1999, p. 274-283, Vol. 19, No. 1
Division of Toxicology and Center for
Environmental Health Sciences, Whitaker College of Health Sciences and
Technology, Massachusetts Institute of Technology, Cambridge,
Massachusetts 02139
Received 8 September 1998/Accepted 12 October 1998
Transient transfection of rodent fibroblasts with plasmids carrying
a full-size pro-
0270-7306/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Transcriptional and Posttranscriptional Silencing
of Rodent
1(I) Collagen by a Homologous Transcriptionally
Self-Silenced Transgene
and
1(I) collagen gene (pWTC1) results in rapid
reduction of the endogenous transcripts by >90%, while the transgene
mRNA is undetectable. Using deletion constructs, two adjacent 5'
noncoding regions of the gene are identified as causing transcriptional
silencing of the endogene in normal and v-fos-transformed cells but not in nontumorigenic revertants, which show partial relief
from v-fos transformation-induced
1(I) gene suppression. The 3' end of the transgene carries an additional element(s), causing
posttranscriptional silencing of the endogene in all cells including
the revertant. Data indicate that the transgenes are transcriptionally
self-silenced. Genome-integrated transgenes that are transcriptionally
active also allow expression of the endogene, suggesting gene
activation by chromosomal factors missing in pWTC1. Silencing is not
regulated by antisense RNA. Silencing of the endogenous pro-
1(I)
collagen gene is not linked to the level of transgene expression.
*
Corresponding author. Present address: Fred Hutchinson
Cancer Research Center, Seattle, WA 98109-1024. Phone: (206) 667-4107. Fax: (206) 667-5815. E-mail: hzarbl{at}fred.fhcrc.org.
Present address: VION Pharmaceuticals, Inc., New Haven, CT 06511.
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