Nucleic Acids Research, Vol 24, Issue 16 3235-3241, Copyright © 1996 by Oxford University Press
PC Brown and JA Silverman
The mdr2 gene encodes a P-glycoprotein that transports phospholipids across
the canalicular membrane in hepatocytes. In this report we describe the
isolation, sequencing and first functional characterization of the promoter
of mdr2. Analysis of 1.6 kb of DNA upstream of the initiation of
translation revealed that this sequence has a high GC content, lacks a TATA
element and contains a number of putative transcription factor binding
sites. We observed that transcription initiates at several sites between
-290 and -463 and that this region was critical for promoter activity. Gel
mobility shift assays indicated that Sp1 protein binds to a Sp1 consensus
site located at -263. Co-expression of Sp1 protein with a reporter
construct containing the -263 GC box demonstrated that Sp1 regulates
transcription of this promoter. Expression of a non-functional Sp1 protein
did not increase transcription from the mdr2 promoter. Mutation of the -263
GC box diminished the response of the promoter to Sp1 protein. Mutation of
this site also decreased expression of this promoter in cells which
normally express this gene. These data show that Spl has a role in the
regulation of mdr2 expression.
ARTICLES
Characterization of the rat mdr2 promoter and its regulation by the transcription factor Sp1
Laboratory of Experimental Carinogenesis, National Cancer Institute, Bethesda, MD 20892-4255. USA.
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