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Molecular and Cellular Biology, September 2001, p. 5710-5722, Vol. 21, No. 17
Department of Biological Sciences, University
of Pittsburgh, Pittsburgh, Pennsylvania 152601;
Department of Biological Sciences, Carnegie Mellon
University, Pittsburgh, Pennsylvania 152132; and
SFB Biomembrane Research Center, Institut für
Biochemie, TU Graz, A8010 Graz, Austria3
Received 31 January 2001/Returned for modification 14 March
2001/Accepted 5 June 2001
Mutations in the Saccharomyces cerevisiae SNF1 gene
affect a number of cellular processes, including the expression of
genes involved in carbon source utilization and phospholipid
biosynthesis. To identify targets of the Snf1 kinase that modulate
expression of INO1, a gene required for an early,
rate-limiting step in phospholipid biosynthesis, we performed a genetic
selection for suppressors of the inositol auxotrophy of
snf1
0270-7306/01/$04.00+0 DOI: 10.1128/MCB.21.17.5710-5722.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Inhibition of Acetyl Coenzyme A Carboxylase Activity Restores
Expression of the INO1 Gene in a snf1
Mutant Strain of Saccharomyces cerevisiae
and
strains. We identified mutations in
ACC1 and FAS1, two genes important for
fatty acid biosynthesis in yeast; ACC1 encodes acetyl
coenzyme A carboxylase (Acc1), and FAS1 encodes the
subunit of fatty acid synthase. Acc1 was shown previously to be
phosphorylated and inactivated by Snf1. Here we show that
snf1
strains with increased Acc1 activity exhibit decreased INO1 transcription. Strains carrying the
ACC1 suppressor mutation have reduced Acc1 activity in
vitro and in vivo, as revealed by enzymatic assays and increased
sensitivity to the Acc1-specific inhibitor soraphen A. Moreover, a
reduction in Acc1 activity, caused by addition of soraphen A, provision
of exogenous fatty acid, or conditional expression of
ACC1, suppresses the inositol auxotrophy of
snf1
strains. Together, these findings indicate that
the inositol auxotrophy of snf1
strains arises in
part from elevated Acc1 activity and that a reduction in this activity
restores INO1 expression in these strains. These results
reveal a Snf1-dependent connection between fatty acid production and
phospholipid biosynthesis, identify Acc1 as a Snf1 target important for
INO1 transcription, and suggest models in which
metabolites that are generated or utilized during fatty acid
biosynthesis can significantly influence gene expression in yeast.
*
Corresponding author. Mailing address: Department of
Biological Sciences, University of Pittsburgh, 269 Crawford Hall,
Pittsburgh, PA 15260. Phone: (412) 624-6963. Fax: (412) 624-4759. E-mail: arndt{at}pitt.edu.
Present address: Department of Molecular Biology and Genetics,
Cornell University, Ithaca, NY 14853.
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