摘要
Cepo(centrosomal protein oncogene)是我们实验室从人胎肝cDNA文库中克隆到的一个未知功能的新基因。cepo在进化过程中高度保守，但各物种中的同源基因目前均无任何功能信息。
人cepo基因的染色体定位为10q24.2，其基因组序列大约为14kb，cepo通过选择性剪接产生cepo-A和cepo-B两种转录本，两种转录本大小相同，为1.5kb。cepo—A由4个外显子组成、cepo—B由5个外显子组成；cepo-A和cepo—B的所有内含子／外显子剪接边界均符合典型的GT／AG剪接模式。
cepo基因的组织表达谱结果表明，它具有类似看家基因的广泛表达的特征；cepo-A和cepo-B分别编码99和142个氨基酸。在这两种蛋白质异构体的C末端均存在一个亮氨酸拉链结构域。
CEPO大部分定位于细胞质中，一部分定位于中心体上；其中心体定位表现出不依赖于细胞周期变化的方式，即在细胞周期的各个时期(G1-S-G2-M)，CEPO都定位于中心体上。
CEPO在NIH3T3细胞中异源过表达可引起此细胞的中心体扩增。通过软琼脂集落形成实验、裸鼠皮下细胞接种实验，我们证明CEPO的这种异源过表达还可以引起被稳定转染的NIH3T3细胞发生恶性转化。运用免疫组化组织芯片实验，我们证明：CEPO在某些肿瘤组织中的表达水平明显高于各自相应的正常对照组织表明CEPO具有原癌基因的属性，该基因的名称——cepo即由此而来。运用免疫组化组织芯片实验，我们证明：CEPO在某些肿瘤组织中的表达水平明显高于各自相应的正常对照组织。
利用CEPO做诱饵蛋白筛选人睾丸cDNA文库得到大量阳性克隆。通过进一步的体内、外相互作用验证，我们发现CEPO与KIF3A(Kinesin family member 3A)和JAB1(c-Jun activating domain-binding protein 1)之间的相互作用是真实存在的。CEPO通过与JAB1的相互作用参与了JAB1介导的信号转导，并通过JAB1增强AP-1的转录活性。
Cepo (centrosomal protein oncogene) is a novel human gene isolated from the cDNA library of fetal liver, highly conserved in evolution, and there is no idea about the function of its homologeous genes among species.
The human cepo gene was mapped on 10q24.2 and spanned about 14 kb. The two cDNA isoforms-cepo-A and cepo-B were produced by alternative splicing on the 5'-terminus of cepo gene, the size of two cDNA isoforms of cepo was same and was about 1.5kb. The human cepo-A and cepo-B are composed of 4 and 5 exons respectively, the sequences of the intron/exon junctions were all exactly consistent with the typical GT/AG consensus motif of the splice donor and acceptor sites.
Cepo is widely expressed and with a feature of housekeeping gene. The two cDNA isoforms-cepo-A and cepo-B code 99 and 142 animo acid polypeptides respectively, a leucine zipper sequence pattern existed in the C-terminus of these two protein isoforms.
CEPO was located mainly at cytoplasm and centrosome of cultured cells in the manner of independence of cell cycle.
The ectopic overexpression of this gene in NIH3T3 cells could induce centrosome amplification. Subsequently, the ectopic overexpression of CEPO could induce cell transformation malignantly was confirmed by soft agar growth assay and tumofigenesis in nude mice assays. The protein level of CEPO in some malignant tumors is significantly higher than corresponding normal tissues. Taken together, we reveiled that cepo is an oncogene and named it as cepo.
We used the full length CEPO-A and CEPO-B as "bait" in a yeast two-hybrid system to screen a human testis cDNA library, and identified several types of clones. The protein-protein interaction between CEPO and KIF3A (kinesin family member 3A), CEPO and JAB1 (c-Jun activating domain-binding protein 1) were confirmed by in vitro and in vivo interaction binding assays. It was further demonstrated that CEPO enhanced AP-1 activity through signal transduction mediated by JAB1.
引文
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