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Mol. Cell. Biol., 05 1997, 2485-2496, Vol 17, No. 5
B Santos, A Duran and MH Valdivieso
The CHS5 locus of Saccharomyces cerevisiae is important for wild-type
levels of chitin synthase III activity. chs5 cells have reduced levels of
this activity. To further understand the role of CHS5 in yeast, the CHS5
gene was cloned by complementation of the Calcofluor resistance phenotype
of a chs5 mutant. Transformation of the mutant with a plasmid carrying CHS5
restored Calcofluor sensitivity, wild-type cell wall chitin levels, and
chitin synthase III activity levels. DNA sequence analysis reveals that
CHS5 encodes a unique polypeptide of 671 amino acids with a molecular mass
of 73,642 Da. The predicted sequence shows a heptapeptide repeated 10
times, a carboxy-terminal lysine-rich tail, and some similarity to
neurofilament proteins. The effects of deletion of CHS5 indicate that it is
not essential for yeast cell growth; however, it is important for mating.
Deletion of CHS3, the presumptive structural gene for chitin synthase III
activity, results in a modest decrease in mating efficiency, whereas
chs5delta cells exhibit a much stronger mating defect. However, chs5 cells
produce more chitin than chs3 mutants, indicating that CHS5 plays a role in
other processes besides chitin synthesis. Analysis of mating mixtures of
chs5 cells reveals that cells agglutinate and make contact but fail to
undergo cell fusion. The chs5 mating defect can be partially rescued by
FUS1 and/or FUS2, two genes which have been implicated previously in cell
fusion, but not by FUS3. In addition, mating efficiency is much lower in
fus1 fus2 x chs5 than in fus1 fus2 x wild type crosses. Our results
indicate that Chs5p plays an important role in the cell fusion step of
mating.
Copyright © 1997, American Society for Microbiology
CHS5, a gene involved in chitin synthesis and mating in Saccharomyces cerevisiae
Instituto de Microbiologia Bioquimica, Consejo Superior de Investigaciones Cientificas/Universidad de Salamanca, Spain.
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