Bidlingmaier S, Weiss E L, Seidel C, Drubin D G, Snyder M
Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06520-8103, USA.
Mol Cell Biol. 2001 Apr;21(7):2449-62. doi: 10.1128/MCB.21.7.2449-2462.2001.
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 cbk1Delta 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 cbk1Delta cells and disrupts the bud neck localization of Cbk1p. Whole-genome transcriptional analysis of cbk1Delta 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 ace2Delta 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.
在出芽的早期阶段，细胞壁重塑和极性分泌集中在芽尖（顶端生长）。CBK1基因编码一种假定的丝氨酸/苏氨酸蛋白激酶，它是在一个旨在分离影响顶端生长的突变的筛选中被鉴定出来的。对cbk1Delta细胞的分析表明，Cbk1p是高效顶端生长、正确的交配突起形态、二倍体细胞中双极芽位点选择以及细胞分离所必需的。表位标记的Cbk1p在后期末期、细胞分离前定位于芽颈两侧。CBK1和另一个基因HYM1先前在一个涉及转录抑制的基因筛选中被鉴定出来，并被认为在同一途径中发挥作用。HYM1的缺失导致与在cbk1Delta细胞中观察到的相似表型，并破坏了Cbk1p在芽颈的定位。对cbk1Delta的全基因组转录分析表明，该激酶调节许多具有细胞壁相关功能的基因的表达，包括高效细胞分离所需的两个基因：几丁质酶编码基因CTS1和葡聚糖酶编码基因SCW11。Ace2p转录因子是CTS1表达所必需的，并且已被证明与Cbk1p发生物理相互作用。对ace2Delta细胞的分析表明，Ace2p是细胞分离所必需的，但不是极性生长所必需的。我们的结果表明，Cbk1p和Hym1p的功能是调节两条不同的细胞形态发生途径：一条不依赖ACE2的途径，它是高效顶端生长和交配突起形成所必需的；另一条依赖ACE2的途径，它是胞质分裂后高效细胞分离所必需的。Cbk1p与粗糙脉孢菌的Cot-1、粟酒裂殖酵母的Orb6、秀丽隐杆线虫、果蝇和人类的Ndr以及果蝇和哺乳动物的WARTS/LATS激酶关系最为密切。许多与Cbk1相关的激酶已被证明可调节细胞形态。
