一个鼻咽癌相关EST的鉴定及其全长cDNA序列分析

Identification of a Nasopharyngeal Carcinoma-related EST and Sequence Analysis of its Full-length cDNA

鼻咽癌是我国南方及东南亚地区常见的恶性肿瘤之一.通过对鼻咽癌染色体高频率杂合性丢失区域3p21的表达序列标签(expressedsequencetag,EST)进行同源性比较分析,运用逆转录聚合酶链式反应的方法,筛选到一个在41.18%(14/34)的鼻咽癌活检组织及20.0%(1/5)的鼻咽癌细胞系中表达下调的ESTBG772301;并用Northern杂交方法,检测了该EST在多种正常成人组织中的表达状况及其所代表基因的转录本大小.在此基础上,对该EST来源的cDNA克隆(IMAGE:4839190)进行直接测序,获得了一个全长为2377bp的新cDNA序列;经生物信息学分析,发现它与已知基因序列无明显同源性,属于一个新基因,定位于染色体3p21.3,被命名为鼻咽癌表达下调基因(NPCEDRG,GenBank登录号:AF538150).其编码的蛋白质含169个氨基酸,与一个已报道的在进化上相对保守、功能未知的人类蛋白Nicolin1(简称NICN1)N端170个氨基酸残基的序列同源性为97%,但缺少NICN1蛋白C端43个氨基酸残基,可能是nicolin1基因不同剪接本的编码产物.

Nasopharyngeal carcinoma （NPC） is a common cancer in Southern China and East-Southern Asia. Loss of heterozygosity （LOH） with high frequency has been found at chromosome 3p21 region in NPC. This study was designed to identify a novel NPC-related cDNA sequence on the basis of expression analysis of expressed sequence tags （ESTs） at chromosome 3p21 in NPC cell lines and biopsy tissues. One of these ESTs, BG772301, was found to be under-expressed in 41.18% （14/34） NPC biopsy tissues and 20.0% （1/5） NPC cell lines with reverse transcription-polymerase chain reaction（RT-PCR）. The expression of EST BG772301 was also detected in multiple normal human tissues by Northern hybridization. A 2 377 bp full-length cDNA sequence that has not significant homology with other known genes in bioinformatic analysis, was obtained by direct sequencing of the cDNA clone（IMAGE： 4839190） from which the EST BG772301 comes. This novel cDNA sequence was termed nasopharyngeal carcinoma expression down-regulated gene （NPCEDRG, GenBank accession number： AF538150） that maps at chromosome 3p21.3 and encodes a protein consisting of 169 amino acids. The amino acid sequence of NPCEDRG protein shows 97% identity to 170 amino acid residues at the N-terminus of a human protein Nicolinl （NICN1）, but lacks 43 amino acid residues at C-terminus of NICN1 protein. NPCEDRG protein may be encoded by an alternative splice variant of nicolinl gene.