Schmidt A, Kunz J, Hall M N
Department of Biochemistry, University of Basel, Switzerland.
Proc Natl Acad Sci U S A. 1996 Nov 26;93(24):13780-5. doi: 10.1073/pnas.93.24.13780.
The Saccharomyces cerevisiae gene TOR2 encodes a putative phosphatidylinositol kinase that has two essential functions. One function is redundant with TOR1, a TOR2 homolog, and is required for signaling translation initiation and early G1 progression. The second essential function is unique to TOR2. Here we report that loss of the TOR2-unique function disrupts polarized distribution of the actin cytoskeleton. A screen for dosage suppressors of a dominant negative TOR2 allele identified TCP20/CCT6, encoding a subunit of the cytosolic chaperonin TCP-1 that is involved in the biogenesis of actin structures. Overexpression of TCP20 restores growth and polarized distribution of the actin cytoskeleton in a tor2 mutant. TCP20 overexpression does not restore growth in a tor1 tor2 double mutant. We suggest that the unique function of the phosphatidylinositol kinase homolog TOR2 is required for signaling organization of the actin cytoskeleton during the cell cycle. TOR2, via its two functions, may thus integrate temporal and spatial control of cell growth.
酿酒酵母基因TOR2编码一种假定的磷脂酰肌醇激酶，该激酶具有两种重要功能。一种功能与TOR2的同源物TOR1冗余，是信号转导翻译起始和早期G1期进程所必需的。第二种重要功能是TOR2所特有的。在此我们报告，TOR2特有的功能丧失会破坏肌动蛋白细胞骨架的极化分布。对显性负性TOR2等位基因的剂量抑制子进行筛选，鉴定出TCP20/CCT6，其编码参与肌动蛋白结构生物合成的胞质伴侣蛋白TCP-1的一个亚基。TCP20的过表达可恢复tor2突变体中肌动蛋白细胞骨架的生长和极化分布。TCP20的过表达不能恢复tor1 tor2双突变体中的生长。我们认为，磷脂酰肌醇激酶同源物TOR2的独特功能是细胞周期中肌动蛋白细胞骨架信号组织所必需的。因此，TOR2可能通过其两种功能整合细胞生长的时间和空间控制。
