人类核糖体S6激酶RPS6KA5的cDNA克隆及组织表达谱分析

人类核糖体S6激酶包括两个蛋白家族P90RSK和P70S6K，它们分别介导着两条细胞信号传导通路。当这些激酶活性被它们的抗体或纳巴霉素抑制时，细胞的增殖随之停止。但当纳巴霉素的结构类似物－免疫抑制剂FK－506作用于细胞时，虽可抑制成纤维细胞PBLl的增殖，但却不能抑制P90RSK、P70S6K和MAPK的活性。这提示体内还存在着已知P90RSK和P70S6K蛋白的替代者或还存在着不涉及已知P90RSK和70S6K的信号通路。为此，本文采用“同源筛选”策略，试图证实上述推测。我们以小鼠P90RSK基因的保守性序列为探针，在NCBIEST数据库中进行同源筛选，得到三个人体同源EST片段。以EST片段的整合序列为探针，在人脑组织cDNA文库中进行杂交筛选，最终获得3833bp的全长cDNA序列，其中第165-2570bp为一完整的开放阅读框，编码了802个氨基酸。这个推导蛋白质与人P90RSK家族成员具有较高氨基酸同源性，并被命名为RPS6KA5，它在国际GenBank的登录号为AF090421，Northern杂交显示该基因在人各组织中广泛表达，RH定位将该基因定于14号染色体长臂31-32．1的范围内，另一新的P70S6K基因(GenBank注册登记号为AF037447)也已被克隆，从而证实了人体内存在着已知P90RSK及P70S6K家族基因替代者的最初设想。

CLONING AND TISSUE EXPRESSIVE PATTERN ANALYSIS OF THE HUMAN RIBOSOMAL S6 KINASE-RPS6KA5 cDNA

Human ribosomal protein S6 kinase includes two protein families; P90RSK and P70S6K,they participate in two different signaling pathways. When the two kinases were inhibited by their antibodies or rapamycin, the proliferation of cells was arrested. However, their analog, the im-munosupressant FK-506, can inhibit the proliferation of fibroblast PBL1 without interfering with the activities of P90RSK, P70S6K and MAPK. We take the tactics of " homolog screening " to demonstrate whether there are some novel proteins which can substitute for the known P90RSK and P70S6K or other pathways without interfering with the known P90RSK and P70S6K. With the conserved sequence of mouse p90RSK as a probe, we screened the homologous sequence in NCBI EST database and got three human EST fragments. With the assembled contig as a probe to screen human brain cDNA library, a full-length cDNA of 3833bp was attained. It contains a completed open reading frame from 165bp to 2570bp encoding 802 amino acids. The putative protein has higher homology with other members of p90RSK family. The gene was named RPS6KA5, the accession number in GenBank is AF090421. Northern hybridization showed the gene expressed in 16 human tissues tested, and the gene was localized in 14q31-32. 1 by RH mapping. Another novel P70S6K gene has also been cloned. Thus, our initial presumption that there is an analog of known P90RSK and P70S6K in human beings was proved.