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Infection and Immunity, January 2001, p. 108-114, Vol. 69, No. 1
Department of Genetics, Cell Biology, and
Development, University of Minnesota, St. Paul, Minnesota 55108
Received 5 May 2000/Returned for modification 31 July 2000/Accepted 18 September 2000
Parasexual genetic analysis of Candida albicans
utilized the dominant selectable marker that conferred resistance to
mycophenolic acid. We cloned and sequenced the
IMH3r gene from C. albicans strain
1006, which was previously identified as resistant to mycophenolic acid
(MPA) (A. K. Goshorn and S. Scherer, Genetics 123:213-218, 1989).
MPA is an inhibitor of IMP dehydrogenase, an enzyme necessary for the
de novo biosynthesis of GMP. G. A. Kohler et al. (J. Bacteriol. 179:2331-2338, 1997) have shown that the wild-type
IMH3 gene, when expressed in high copy number, will confer
resistance to this antibiotic. We demonstrate that the
IMH3r gene from strain 1006 has three amino
acid changes, two of which are nonconservative, and demonstrate that at
least two of the three mutations are required to confer resistance to
MPA. We used this gene as a dominant selectable marker in clinical
isolates of C. albicans and Candida tropicalis.
We also identified the presence of autonously replicating sequence
elements that permit autonomous replication in the promoter region of
this gene. Finally, we found the excision of a
0019-9567/01/$04.00+0 DOI: 10.1128/IAI.69.1.108-114.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Single-Copy IMH3 Allele Is Sufficient To Confer
Resistance to Mycophenolic Acid in Candida albicans and To
Mediate Transformation of Clinical Candida Species
-type long terminal
repeat element outside the IMH3 open reading frame of the
gene in some strains. We used the IMH3r allele
to disrupt one allele of ARG4 in two clinical isolates, WO-1 and FC18, thus demonstrating that a single ectopic integration of
this dominant selectable marker is sufficient to confer resistance to MPA.
*
Corresponding author. Mailing address: Department of
Genetics, Cell Biology, and Development, University of Minnesota,
St. Paul, MN 55108. Phone: (612) 625-4732. Fax: (612) 625-5754. E-mail: ptm{at}biosci.cbs.umn.edu.
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