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Molecular and Cellular Biology, May 2000, p. 3245-3255, Vol. 20, No. 9
Departamento de Microbiología II,
Facultad de Farmacia, Universidad Complutense de Madrid, 28040 Madrid,
Spain
Received 21 June 1999/Returned for modification 19 August
1999/Accepted 4 February 2000
The Saccharomyces cerevisiae Ygr189c, Yel040w, and
Ylr213c gene products show significant homologies among themselves and with various bacterial
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Copyright © 2000, American Society for Microbiology. All rights reserved.
A Novel Family of Cell Wall-Related Proteins
Regulated Differently during the Yeast Life Cycle
-glucanases and eukaryotic
endotransglycosidases. Deletion of the corresponding genes, either
individually or in combination, did not produce a lethal phenotype.
However, the removal of YGR189c and YEL040w,
but not YLR213c, caused additive sensitivity to compounds
that interfere with cell wall construction, such as Congo red and
Calcofluor White, and overexpression of YEL040w led to
resistance to these compounds. These genes were renamed
CRH1 and CRH2, respectively, for Congo red
hypersensitive. By site-directed mutagenesis we found that the putative
glycosidase domain of CRH1 was critical for its function in
complementing hypersensitivity to the inhibitors. The involvement of
CRH1 and CRH2 in the development of cell wall
architecture was clearly shown, since the alkali-soluble glucan
fraction in the crh1
crh2
strain was almost twice the
level in the wild-type. Interestingly, the three genes were subject to
different patterns of transcriptional regulation. CRH1 and
YLR213c (renamed CRR1, for CRH
related) were found to be cell cycle regulated and also expressed under
sporulation conditions, whereas CRH2 expression did not
vary during the mitotic cycle. Crh1 and Crh2 are localized at the cell
surface, particularly in chitin-rich areas. Consistent with the
observed expression patterns, Crh1-green fluorescent protein was found
at the incipient bud site, around the septum area in later stages of
budding, and in ascospore envelopes. Crh2 was found to localize mainly
at the bud neck throughout the whole budding cycle, in mating
projections and zygotes, but not in ascospores. These data suggest that
the members of this family of putative glycosidases might exert a common role in cell wall organization at different stages of the yeast
life cycle.
*
Corresponding author. Mailing address: Departamento de
Microbiología II, Facultad de Farmacia, Universidad Complutense
de Madrid, 28040 Madrid, Spain. Phone: 34 91 3941746. Fax: 34 91 3941745. E-mail: jarroyo{at}eucmax.sim.ucm.es.
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