Yang P, Kansra S, Pimental R A, Gilbreth M, Marcus S
Department of Molecular Genetics, University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, USA.
J Biol Chem. 1998 Jul 17;273(29):18481-9. doi: 10.1074/jbc.273.29.18481.
We describe the characterization of a novel gene, shk2, encoding a second p21(cdc42/rac)-activated protein kinase (PAK) homolog in fission yeast. Like other known PAKs, Shk2 binds to Cdc42 in vivo and in vitro. While overexpression of either shk2 or cdc42 alone does not impair growth of wild type fission yeast cells, cooverexpression of the two genes is toxic and leads to highly aberrant cell morphology, providing evidence for functional interaction between Cdc42 and Shk2 proteins in vivo. Fission yeast shk2 null mutants are viable and exhibit no obvious phenotypic defects. Overexpression of shk2 restores viability and normal morphology but not full mating competence to fission yeast cells carrying a shk1 null mutation. Additional genetic data suggest that Shk2, like Cdc42 and Shk1, participates in Ras-dependent morphological control and mating response pathways in fission yeast. We also show that overexpression of byr2, a gene encoding a Ste11/MAPK kinase kinase homolog, suppresses the mating defect of cells partially defective for Shk1 function, providing evidence of a link between PAKs and mitogen-activated protein kinase signaling in fission yeast. Taken together, our results suggest that Shk2 is partially overlapping in function with Shk1, with Shk1 being the dominant protein in function.
我们描述了一个新基因shk2的特征，该基因在裂殖酵母中编码第二个p21（cdc42/rac）激活的蛋白激酶（PAK）同源物。与其他已知的PAK一样，Shk2在体内和体外均与Cdc42结合。虽然单独过表达shk2或cdc42不会损害野生型裂殖酵母细胞的生长，但这两个基因的共过表达是有毒的，并导致高度异常的细胞形态，这为Cdc42和Shk2蛋白在体内的功能相互作用提供了证据。裂殖酵母shk2缺失突变体是有活力的，并且没有明显的表型缺陷。shk2的过表达恢复了携带shk1缺失突变的裂殖酵母细胞的活力和正常形态，但没有恢复完全的交配能力。其他遗传数据表明，Shk2与Cdc42和Shk1一样，参与裂殖酵母中Ras依赖性的形态控制和交配反应途径。我们还表明，编码Ste11/MAPK激酶激酶同源物的基因byr2的过表达抑制了Shk1功能部分缺陷的细胞的交配缺陷，这为裂殖酵母中PAK与丝裂原活化蛋白激酶信号传导之间的联系提供了证据。综上所述，我们的结果表明，Shk2在功能上与Shk1部分重叠，其中Shk1在功能上是主要的蛋白。
