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Molecular and Cellular Biology, April 2001, p. 2449-2462, Vol. 21, No. 7
Department of Molecular, Cellular, and
Developmental Biology, Yale University, New Haven, Connecticut
06520-8103,1 and Department of Molecular
and Cell Biology, University of California, Berkeley, Berkeley,
California 94720-32022
Received 28 August 2000/Returned for modification 20 October
2000/Accepted 17 January 2001
During the early stages of budding, cell wall remodeling and
polarized secretion are concentrated at the bud tip (apical growth). The CBK1 gene, encoding a putative serine/threonine protein
kinase, was identified in a screen designed to isolate mutations that affect apical growth. Analysis of cbk1
0270-7306/01/$04.00+0 DOI: 10.1128/MCB.21.7.2449-2462.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
The Cbk1p Pathway Is Important for Polarized Cell
Growth and Cell Separation in Saccharomyces
cerevisiae
cells reveals
that Cbk1p is required for efficient apical growth, proper mating
projection morphology, bipolar bud site selection in diploid cells, and
cell separation. Epitope-tagged Cbk1p localizes to both sides of the bud neck in late anaphase, just prior to cell separation.
CBK1 and another gene, HYM1, were previously
identified in a screen for genes involved in transcriptional
repression and proposed to function in the same pathway. Deletion of
HYM1 causes phenotypes similar to those observed in
cbk1
cells and disrupts the bud neck localization of
Cbk1p. Whole-genome transcriptional analysis of cbk1
suggests that the kinase regulates the expression of a number of genes
with cell wall-related functions, including two genes required for
efficient cell separation: the chitinase-encoding gene CTS1
and the glucanase-encoding gene SCW11. The Ace2p
transcription factor is required for expression of CTS1 and
has been shown to physically interact with Cbk1p. Analysis of
ace2
cells reveals that Ace2p is required for cell
separation but not for polarized growth. Our results suggest that Cbk1p
and Hym1p function to regulate two distinct cell morphogenesis
pathways: an ACE2-independent pathway that is required for
efficient apical growth and mating projection formation and an
ACE2-dependent pathway that is required for efficient cell
separation following cytokinesis. Cbk1p is most closely related to the
Neurospora crassa Cot-1; Schizosaccharomyces pombe Orb6; Caenorhabditis elegans, Drosophila, and
human Ndr; and Drosophila and mammalian WARTS/LATS
kinases. Many Cbk1-related kinases have been shown to regulate cellular morphology.
*
Corresponding author. Mailing address: Department of
Molecular, Cellular, and Developmental Biology, Yale University, P.O. Box 208103, New Haven, CT 06520-8103. Phone: (203) 432-6139. Fax: (203)
432-6161. E-mail: Michael.Snyder{at}yale.edu.
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