Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, Wuhan University, Wuhan, 430072, China.
Hubei Provincial Cooperative Innovation Center of Industrial Fermentation, Wuhan, China.
Curr Genet. 2020 Dec;66(6):1101-1115. doi: 10.1007/s00294-020-01093-9. Epub 2020 Jul 12.
Boi1 and Boi2 are paralogous proteins essential for bud formation in budding yeast. So far, the domains that target Boi1/Boi2 to the polarity sites and function in bud formation are not well understood. Here, we report that a coiled-coil domain of Boi2 cooperates with the adjacent PH domain to confer Boi2's bud-cortex localization and major function in cell growth. The PH domain portion of the PH-CC bi-domain interacts with the Rho GTPases Cdc42 and Rho3 and both interactions are independent of the GTP/GDP-bound state of each GTPase. Interestingly, high-copy RHO3 and BOI2 but not CDC42 suppressed the growth defect of RGA1-C538 overexpression and the sec15-1 mutant and this BOI2 function depends on RHO3, suggesting that Boi2 may function in the Rho3 pathway. The SAM domain of Boi2 plays an essential role in high-copy suppression of the two mutants as well as in the early bud-neck localization of Boi2. The SAM domain and the CC domain also interact homotypically. They are likely involved in the formation of Boi2-containing protein complex. Our results provide new insights in the localization and function of Boi2 and highlight the importance of the PH-CC bi-domain and the SAM domain in Boi2's localization and function.
Boi1 和 Boi2 是芽殖酵母出芽形成所必需的同源蛋白。迄今为止，将 Boi1/Boi2 靶向极性位点并在芽形成中发挥作用的结构域还没有得到很好的理解。在这里，我们报告 Boi2 的卷曲螺旋结构域与相邻的 PH 结构域合作，赋予 Boi2 在芽皮质中的定位和在细胞生长中的主要功能。双域 PH-CC 结构域的 PH 结构域部分与 Rho GTPases Cdc42 和 Rho3 相互作用，并且这两种相互作用都不依赖于每种 GTPase 的 GTP/GDP 结合状态。有趣的是，高拷贝 RHO3 和 BOI2 但不是 CDC42 抑制了 RGA1-C538 过表达和 sec15-1 突变体的生长缺陷，并且该 BOI2 功能依赖于 RHO3，表明 Boi2 可能在 Rho3 途径中发挥作用。Boi2 的 SAM 结构域在高拷贝抑制这两种突变体以及 Boi2 的早期芽颈定位中起着至关重要的作用。SAM 结构域和 CC 结构域也相互作用。它们可能参与了 Boi2 蛋白复合物的形成。我们的研究结果为 Boi2 的定位和功能提供了新的见解，并强调了 PH-CC 双域和 SAM 结构域在 Boi2 的定位和功能中的重要性。
