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J. Biol. Chem., Vol. 275, Issue 38, 29368-29376, September 22, 2000
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From the Department of Cell and Molecular Biology-Microbiology,
Lundberg Laboratory, Göteborg University, Medicinaregatan 9C,
S-413 90 Göteborg, Sweden
Mechanisms involved in transcriptional regulation
of the osmotically controlled GPD1 gene in
Saccharomyces cerevisiae were investigated by promoter
analysis. The GPD1 gene encodes
NAD+-dependent glycerol-3-phosphate
dehydrogenase, a key enzyme in the production of the compatible solute
glycerol. By analysis of promoter deletions, we identified a region at
nucleotides
Rap1p-binding Sites in the Saccharomyces cerevisiae
GPD1 Promoter Are Involved in Its Response to NaCl*
,
478 to
324, in relation to start of translation, to be
of great importance for both basal activity and osmotic induction of
GPD1. Electrophoretic mobility shift and DNase I footprint
analyses demonstrated protein binding to parts of this region that
contain three consensus sequences for Rap1p (repressor
activator protein 1)-binding sites.
Actual binding of Rap1p to this region was confirmed by demonstrating enhanced electrophoretic mobility of the protein-DNA complex with extracts containing an N-terminally truncated version of Rap1p. The
detected Rap1p-DNA interactions were not affected by changes in the
osmolarity of the growth medium. Specific inactivation of the
Rap1p-binding sites by a C-to-A point mutation in the core of the
consensus showed that this factor is a major determinant of
GPD1 expression since mutations in all three putative
binding sites for Rap1p strongly hampered osmotic induction and
drastically lowered basal activity. We also show that the Rap1p-binding
sites appear functionally distinct; the most distal site (core of the consensus at position
386) exhibited the highest affinity for Rap1p
and was strictly required for low salt induction (
0.6 M NaCl), but not for the response at higher salinities (
0.8
M NaCl). This indicates that different molecular mechanisms
might be operational for low and high salt responses of the
GPD1 promoter.
*
This work was supported by grants from the Swedish National
Board for Technical Development and the Swedish National Board for
Natural Science.The costs of publication of this
article were defrayed in part by the
payment of page charges. The article
must therefore be hereby marked
"advertisement" in
accordance with 18 U.S.C. Section
1734 solely to indicate this fact.
Present address: Dept. of Oncological Science, University of Utah,
50 North Medical Dr., Salt Lake City, UT 84132.
§
To whom correspondence should be addressed. Tel.: 46-31-773-2589;
Fax: 46-31-773-2599; E-mail: anders.blomberg@gmm.gu.se.
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