Manning B D, Padmanabha R, Snyder M
Department of Biology, Yale University, New Haven, Connecticut 06520-8103, USA.
Mol Biol Cell. 1997 Oct;8(10):1829-44. doi: 10.1091/mbc.8.10.1829.
Rom2p is a GDP/GTP exchange factor for Rho1p and Rho2p GTPases; Rho proteins have been implicated in control of actin cytoskeletal rearrangements. ROM2 and RHO2 were identified in a screen for high-copy number suppressors of cik1 delta, a mutant defective in microtubule-based processes in Saccharomyces cerevisiae. A Rom2p::3XHA fusion protein localizes to sites of polarized cell growth, including incipient bud sites, tips of small buds, and tips of mating projections. Disruption of ROM2 results in temperature-sensitive growth defects at 11 degrees C and 37 degrees C. rom2 delta cells exhibit morphological defects. At permissive temperatures, rom2 delta cells often form elongated buds and fail to form normal mating projections after exposure to pheromone; at the restrictive temperature, small budded cells accumulate. High-copy number plasmids containing either ROM2 or RHO2 suppress the temperature-sensitive growth defects of cik1 delta and kar3 delta strains. KAR3 encodes a kinesin-related protein that interacts with Cik1p. Furthermore, rom2 delta strains exhibit increased sensitivity to the microtubule depolymerizing drug benomyl. These results suggest a role for Rom2p in both polarized morphogenesis and functions of the microtubule cytoskeleton.
Rom2p是Rho1p和Rho2p GTP酶的GDP/GTP交换因子；Rho蛋白参与肌动蛋白细胞骨架重排的调控。ROM2和RHO2是在筛选酿酒酵母中cik1δ（一种在基于微管的过程中存在缺陷的突变体）的高拷贝数抑制子时被鉴定出来的。一种Rom2p::3XHA融合蛋白定位于极化细胞生长的位点，包括初始芽位点、小芽的尖端和交配突起的尖端。ROM2的破坏导致在11摄氏度和37摄氏度时出现温度敏感型生长缺陷。rom2δ细胞表现出形态缺陷。在允许温度下，rom2δ细胞经常形成细长的芽，并且在接触信息素后无法形成正常的交配突起；在限制温度下，小芽细胞会积累。含有ROM2或RHO2的高拷贝数质粒可抑制cik1δ和kar3δ菌株的温度敏感型生长缺陷。KAR3编码一种与驱动蛋白相关的蛋白，它与Cik1p相互作用。此外，rom2δ菌株对微管解聚药物苯菌灵表现出更高的敏感性。这些结果表明Rom2p在极化形态发生和微管细胞骨架的功能中都发挥作用。
