Affiliation:
1. Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06520-8103, 1 and
2. Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, California 94720-32022
Abstract
ABSTRACT
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
cbk1Δ
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
cbk1Δ
cells and disrupts the bud neck localization of Cbk1p. Whole-genome transcriptional analysis of
cbk1Δ
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
ace2Δ
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.
Publisher
American Society for Microbiology
Subject
Cell Biology,Molecular Biology
Cited by
159 articles.
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