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Molecular and Cellular Biology, September 2001, p. 6161-6169, Vol. 21, No. 18
Hematology Division, Department of Medicine,
Brigham & Women's Hospital, and Harvard Medical School, Boston,
Massachusetts 02115,1 and Nelson
Biological Laboratory, Bureau of Biological Research, Department of
Cell Biology and Neuroscience, Rutgers University, Busch Campus,
Piscataway, New Jersey 088542
Received 3 May 2001/Returned for modification 30 May 2001/Accepted 12 June 2001
Eukaryotes have the ability to respond to changes in oxygen
tension by alterations in gene expression. For example,
OLE1 expression in Saccharomyces
cerevisiae is upregulated under hypoxic conditions. Previous
studies have suggested that the pathway regulating OLE1 expression by unsaturated fatty acids may involve Mga2p and
Spt23p, two structurally and functionally related proteins. To
define the possible roles of each of these genes on hypoxia-induced
OLE1 expression, we examined OLE1
expression under normoxia, hypoxia, and cobalt treatment conditions in
0270-7306/01/$04.00+0 DOI: 10.1128/MCB.21.18.6161-6169.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
MGA2 Is Involved in the Low-Oxygen Response
Element-Dependent Hypoxic Induction of Genes in
Saccharomyces cerevisiae

mga2 or
spt23 deletion
strains. The results of OLE1
promoter-lacZ reporter gene and Northern blot analyses
showed that hypoxia- and cobalt-induced OLE1 expression was dramatically decreased in a
mga2 strain but not
in a
spt23 strain. Further analyses using low-oxygen
response element (LORE)-CYC1-lacZ fusion
reporter assays and electrophoretic mobility shift assays (EMSAs) demonstrated that MGA2 significantly
affects the LORE-dependent hypoxic induction pathway of gene
expression. When MGA2 was supplied by a plasmid, the
LORE-dependent hypoxia-inducible reporter expression was recovered, as
was the hypoxia-inducible complex in EMSAs in the S.
cerevisiae
mga2 strain. Supershift analysis
of EMSAs using crude extracts containing mycMga2p indicated that Mga2p
is a component of the LORE-binding complex. Another LORE-dependent,
hypoxia-inducible gene, ATF1, was similarly affected in
the
mga2 strain. These results indicate that
MGA2 is required for the LORE-dependent hypoxic gene
induction in S. cerevisiae.
*
Corresponding author. Mailing address: Hematology
Division, Department of Medicine, Brigham & Women's Hospital, Harvard
Medical School, 221 Longwood Ave., Boston, MA 02115. Phone: (617)
732-5841. Fax: (617) 739-0748. E-mail:
Mark.Goldberg{at}genzyme.com.
Present address: Department of Adult Oncology, Dana-Farber Cancer
Institute, Department of Medicine, Brigham and Women's Hospital, and
Harvard Medical School, Boston, MA 02115.
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