Pomerening J R, Valente L, Kinzy T G, Jacobs T W
Department of Molecular Pharmacology, Stanford University School of Medicine, 269 West Campus Drive, CCSR 3160, Stanford, CA 94305-5174, USA.
Mol Genet Genomics. 2003 Sep;269(6):776-88. doi: 10.1007/s00438-003-0888-1. Epub 2003 Jul 30.
Elongation factor subunit eEF1Bbeta (formerly EF-1beta in plants and EF-1delta in animals) was identified and cloned in a screen for proteins from pea that interact with a cyclin-dependent kinase (CDK). CDKs are enzymes that regulate progression through meiotic and mitotic cell cycles in eukaryotes. eEF1Bbeta and the related protein eEF1Balpha (formerly EF-1beta' in plants and EF-1beta in animals and fungi) can catalyze GTP/GDP exchange on the G-protein eEF1A (formerly EF-1alpha in plants, animals and fungi) during the elongation phase of protein synthesis in eukaryotes. Recombinant Cdc2 and its native homologues from pea extracts associated both in vitro and in vivo with eEF1Bbeta. A Cdc2-cyclin B complex phosphorylated recombinant plant eEF1Bbetas, but not eEF1Balpha. These interactions between CDK and eEF1Bbeta prompted investigations into the in vivo consequences of this relationship. Expression of cDNAs encoding rice or pea eEF1Bbeta subunits failed to complement a Saccharomyces cerevisiae mutant deleted for the eEF1Balpha gene, as was previously observed for the human eEF1Bbeta. However, replacement of Thr91, the sole consensus CDK phosphorylation site in pea eEF1Bbeta, with alanine allowed the pea protein to substitute for eEF1Balpha function in vivo. In addition, this rescued strain was severely cold sensitive, and more sensitive to translational inhibitors than wild-type yeast. Taken together, these results suggest a physiological connection between the cyclin-dependent class of kinases and a translational elongation factor in mitotic cells, and provide the first in vivo evidence that an altered form of eEF1Bbeta can serve as the guanine nucleotide exchange factor for eEF1A.
延伸因子亚基eEF1Bβ（以前在植物中称为EF-1β，在动物中称为EF-1δ）是在筛选与细胞周期蛋白依赖性激酶（CDK）相互作用的豌豆蛋白时被鉴定和克隆的。CDK是调节真核生物减数分裂和有丝分裂细胞周期进程的酶。在真核生物蛋白质合成的延伸阶段，eEF1Bβ和相关蛋白eEF1Bα（以前在植物中称为EF-1β'，在动物和真菌中称为EF-1β）可以催化G蛋白eEF1A（以前在植物、动物和真菌中称为EF-1α）上的GTP/GDP交换。重组Cdc2及其来自豌豆提取物的天然同源物在体外和体内都与eEF1Bβ相关联。Cdc2-细胞周期蛋白B复合物使重组植物eEF1Bβ磷酸化，但不使eEF1Bα磷酸化。CDK与eEF1Bβ之间的这些相互作用促使人们研究这种关系在体内的后果。编码水稻或豌豆eEF1Bβ亚基的cDNA的表达未能补充缺失eEF1Bα基因的酿酒酵母突变体，就像之前观察到的人类eEF1Bβ一样。然而，将豌豆eEF1Bβ中唯一的共有CDK磷酸化位点Thr91替换为丙氨酸，使得豌豆蛋白能够在体内替代eEF1Bα的功能。此外，这种拯救的菌株对低温极其敏感，并且比野生型酵母对翻译抑制剂更敏感。综上所述，这些结果表明有丝分裂细胞中细胞周期蛋白依赖性激酶类与翻译延伸因子之间存在生理联系，并提供了首个体内证据，即eEF1Bβ的一种改变形式可以作为eEF1A的鸟嘌呤核苷酸交换因子。
