Hu E, Rubin C S
Department of Molecular Pharmacology, Atran Laboratories, Albert Einstein College of Medicine, Bronx, New York 10461.
J Biol Chem. 1990 Mar 25;265(9):5072-80.
The nematode Caenorhabditis elegans provides a model system for investigating the structure, function, and regulation of casein kinase II. Cytosols from C. elegans embryos and gravid adults, which contain fertilized eggs and embryos, are enriched in casein kinase II activity; cytosols from newly hatched larva, four subsequent larval stages, and immature adults exhibit casein kinase II levels that are 3-10-fold lower than those observed in embryo cytosol. C. elegans casein kinase II contains alpha (Mr = 42,000) and beta (Mr = 29,000) subunits and has a Stokes radius of 50 nm. The enzyme utilizes ATP and GTP as substrates, is potently inhibited by heparin and undergoes autophosphorylation. Sequence analyses of cloned cDNAs corresponding to the 1.7-kilobase mRNA encoding the alpha (catalytic) subunit of casein kinase II indicate that the alpha polypeptide contains 359 amino acid residues. Variations in the abundance of casein kinase II alpha mRNA are coordinated with changes in enzyme activity during C. elegans development, indicating that alpha subunit expression is controlled at a pretranslational level. However, the magnitude of the developmentally controlled changes in phosphotransferase activity exceeded the corresponding increments in alpha subunit mRNA content. This suggests that translational and/or post-translational mechanisms also play an important role in the developmental regulation of C. elegans casein kinase II activity. The 2.9-kilobase casein kinase II alpha gene is divided into eight exons by intervening sequences ranging from 48 to 457 base pairs in length. The alpha gene promoter contains a TATA box, and a unique transcription start site has been identified. The intron/exon organization of the casein kinase II alpha gene differs markedly from the gene structure of the catalytic subunit of murine cAMP-dependent protein kinase (Chrivia, J. C., Uhler, M. D., and McKnight, G. S. (1988) J. Biol. Chem. 263, 5739-5744).
线虫秀丽隐杆线虫为研究酪蛋白激酶II的结构、功能及调控提供了一个模型系统。来自秀丽隐杆线虫胚胎和含受精卵及胚胎的妊娠成虫的胞质溶胶富含酪蛋白激酶II活性；来自刚孵化的幼虫、随后的四个幼虫阶段以及未成熟成虫的胞质溶胶中酪蛋白激酶II的水平比胚胎胞质溶胶中观察到的低3至10倍。秀丽隐杆线虫酪蛋白激酶II含有α（Mr = 42,000）和β（Mr = 29,000）亚基，斯托克斯半径为50纳米。该酶以ATP和GTP为底物，被肝素强烈抑制并发生自磷酸化。对与编码酪蛋白激酶IIα（催化）亚基的1.7千碱基mRNA相对应的克隆cDNA进行序列分析表明，α多肽含有359个氨基酸残基。在秀丽隐杆线虫发育过程中，酪蛋白激酶IIα mRNA丰度的变化与酶活性的变化相协调，表明α亚基的表达在转录前水平受到控制。然而，磷酸转移酶活性在发育过程中受控变化的幅度超过了α亚基mRNA含量的相应增加。这表明翻译和/或翻译后机制在秀丽隐杆线虫酪蛋白激酶II活性的发育调控中也起重要作用。2.9千碱基的酪蛋白激酶IIα基因被长度在48至457个碱基对之间的间隔序列分为八个外显子。α基因启动子含有一个TATA盒，并且已确定了一个独特的转录起始位点。酪蛋白激酶IIα基因的内含子/外显子组织与小鼠cAMP依赖性蛋白激酶催化亚基的基因结构明显不同（Chrivia, J. C., Uhler, M. D., and McKnight, G. S. (1988) J. Biol. Chem. 263, 5739 - 5744）。
