Alcorta D A, Crews C M, Sweet L J, Bankston L, Jones S W, Erikson R L
Department of Cellular and Developmental Biology, Harvard University, Cambridge, Massachusetts 02138.
Mol Cell Biol. 1989 Sep;9(9):3850-9. doi: 10.1128/mcb.9.9.3850-3859.1989.
We have previously reported the isolation of cDNAs encoding two closely related Xenopus ribosomal S6 kinases, S6KII alpha and -beta (S. W. Jones, E. Erikson, J. Blenis, J. L. Maller, and R. L. Erikson, Proc. Natl. Acad. Sci. USA 85:3377-3381, 1988). We report here the molecular cloning of one chicken and two mouse homologs of the Xenopus laevis cDNAs. As described for the Xenopus proteins, these cDNAs were found to predict polypeptides that contain two distinct kinase domains, of which one is most closely related to the catalytic subunit of cyclic AMP-dependent protein kinase and the other is most closely related to the catalytic subunit of phosphorylase b kinase. The three predicted proteins were more than 79% identical to the Xenopus S6KII alpha protein. The chicken and one of the mouse cDNAs were, respectively, 3.7 and 3.1 kilobase pairs in length, predicted proteins of 752 and 724 amino acids with molecular weights of 84.4 and 81.6 kilodaltons, and hybridized to mRNAs in fibroblasts and tissues of approximately 3.6 and 3.4 kilobases (kb). The second mouse cDNA was approximately 6.1 kilobase pairs and was not full length but predicted the C-terminal 633 amino acids of a protein that is similar to the C-terminal portion of Xenopus S6KII alpha. This clone hybridized to mRNA transcripts of 7.6 and 3.4 kb. In vitro transcription and translation of the chicken and the mouse cDNAs that predict complete proteins produced major products with apparent molecular weights of 96 and 84 kilodaltons. Analysis of mRNA levels in chicken tissues showed significant quantities of the 3.6-kb transcript in small and large intestine, spleen, and bursa. Both mouse cDNA were similarly expressed at significant levels in intestine, thymus, and lung; however, the 7.6-kb mRNA was differentially and more highly expressed in heart and brain. The two mouse cDNAs represent two different S6 kinase genes, as shown by comparison of their protein sequences, mRNA transcript sizes, genomic organizations, and nucleic acid sequences. We propose that this family of genes be named rsk, for ribosomal S6 kinase.
我们先前已报道了编码两种密切相关的非洲爪蟾核糖体S6激酶S6KIIα和β的cDNA的分离（S.W.琼斯、E.埃里克森、J.布莱尼斯、J.L.马勒和R.L.埃里克森，《美国国家科学院院刊》85:3377 - 3381，1988年）。我们在此报道非洲爪蟾cDNA的一个鸡同源物和两个小鼠同源物的分子克隆。如同对非洲爪蟾蛋白的描述，发现这些cDNA预测的多肽含有两个不同的激酶结构域，其中一个与环磷酸腺苷依赖性蛋白激酶的催化亚基关系最为密切，另一个与磷酸化酶b激酶的催化亚基关系最为密切。这三种预测的蛋白质与非洲爪蟾S6KIIα蛋白的同一性超过79%。鸡和其中一个小鼠cDNA的长度分别为3.7和3.1千碱基对，预测的蛋白质分别为752和724个氨基酸，分子量分别为84.4和81.6千道尔顿，并且与成纤维细胞和组织中大约3.6和3.4千碱基（kb）的mRNA杂交。第二个小鼠cDNA约为6.1千碱基对，不是全长，但预测了一种与非洲爪蟾S6KIIα的C末端部分相似的蛋白质的C末端633个氨基酸。该克隆与7.6和3.4 kb的mRNA转录本杂交。对预测完整蛋白质的鸡和小鼠cDNA进行体外转录和翻译，产生了表观分子量为96和84千道尔顿的主要产物。对鸡组织中mRNA水平的分析表明，在小肠、大肠、脾脏和法氏囊中存在大量3.6 - kb的转录本。两种小鼠cDNA在肠道、胸腺和肺中也有类似的显著表达水平；然而，7.6 - kb的mRNA在心脏和大脑中差异表达且表达水平更高。通过比较它们的蛋白质序列、mRNA转录本大小、基因组结构和核酸序列表明，这两个小鼠cDNA代表两个不同的S6激酶基因。我们建议将这个基因家族命名为rsk，即核糖体S6激酶。
