Sharp Tyson V, Wang Hsei-Wei, Koumi Andrew, Hollyman Daniel, Endo Yoshio, Ye Hongtao, Du Ming-Qing, Boshoff Chris
The CRC Viral Oncology Group, Wolfson Institute for Biomedical Research, University College London, London, United Kingdom WC1E 6BT.
J Virol. 2002 Jan;76(2):802-16. doi: 10.1128/jvi.76.2.802-816.2002.
The Kaposi's sarcoma-associated herpesvirus (KSHV) (or human herpesvirus 8) open reading frame (ORF) K15 encodes a putative integral transmembrane protein in the same genomic location as latent membrane protein 2A of Epstein-Barr virus. Ectopic expression of K15 in cell lines revealed the presence of several different forms ranging in size from full length, approximately 50 kDa, to 17 kDa. Of these different species the 35- and 23-kDa forms were predominant. Mutational analysis of the initiator AUG indicated that translation initiation from this first AUG is required for K15 expression. Computational analysis indicates that the different forms detected may arise due to proteolytic cleavage at internal signal peptide sites. We show that K15 is latently expressed in KSHV-positive primary effusion lymphoma cell lines and in multicentric Castleman's disease. Using a yeast two-hybrid screen we identified HAX-1 (HS1 associated protein X-1) as a binding partner to the C terminus of K15 and show that K15 interacts with cellular HAX-1 in vitro and in vivo. Furthermore, HAX-1 colocalizes with K15 in the endoplasmic reticulum and mitochondria. The function of HAX-1 is unknown, although the similarity of its sequence to those of Nip3 and Bcl-2 infers a role in the regulation of apoptosis. We show here that HAX-1 can form homodimers in vivo and is a potent inhibitor of apoptosis and therefore represents a new apoptosis regulatory protein. The putative functions of K15 with respect to its interaction with HAX-1 are discussed.
卡波西肉瘤相关疱疹病毒(KSHV)(或人类疱疹病毒8型)开放阅读框(ORF)K15在与爱泼斯坦-巴尔病毒潜伏膜蛋白2A相同的基因组位置编码一种假定的整合跨膜蛋白。K15在细胞系中的异位表达显示存在几种不同形式,大小范围从全长约50 kDa到17 kDa。在这些不同的物种中,35 kDa和23 kDa的形式占主导。起始AUG的突变分析表明,从这个第一个AUG开始的翻译起始对于K15的表达是必需的。计算分析表明,检测到的不同形式可能是由于内部信号肽位点的蛋白水解切割所致。我们表明K15在KSHV阳性的原发性渗出性淋巴瘤细胞系和多中心Castleman病中潜伏表达。使用酵母双杂交筛选,我们鉴定出HAX-1(HS1相关蛋白X-1)作为K15 C末端的结合伴侣,并表明K15在体外和体内与细胞HAX-1相互作用。此外,HAX-1与K15在内质网和线粒体中共定位。HAX-1的功能尚不清楚,尽管其序列与Nip3和Bcl-2的序列相似性推断其在细胞凋亡调节中起作用。我们在此表明HAX-1在体内可形成同二聚体,是一种有效的细胞凋亡抑制剂,因此代表一种新的细胞凋亡调节蛋白。讨论了K15与HAX-1相互作用的假定功能。