[Molecular cloning and functional analysis of STGC3 - a novel gene on chromosome 3p21]

A locus of loss of heterozygosity (LOH) with high frequency has been found on chromosome 3p21 in nasopharyngeal carcinoma (NPC). On the basis of our former research, this study was designed to clone and analyze a novel NPC-associated gene at this locus.

The full-length cDNA sequence of this gene was obtained by plasmid cDNA sequencing and RACE,and analyzed by bioinformatics. The pEGFP-C2/STGC3 fusion mammalian expression vector was constructed, and transfected into COS7 and CNE2 cell lines mediated by lipofectin to analyze the subcellular localization of gene expressing proteins. The expression of STGC3 was detected in normal tissues and tumor cell lines by Northern blot.

An 1 271 bp full-length cDNA sequence of gene,which had no obvious homology with other known genes in bioinformatic databases,was obtained. This gene,named STGC3 (GenBank accession number:AY078383), localized on chromosome 3p21, and encodes a protein consisting of 146 amino acids. Protein localization analysis under fluorescent microscope indicated that STGC3 fusion protein was distributed in nucleus and cytoplasm 24-48 hours after transfection. MTE(TM)Array2 Northern blot analysis showed STGC3 expressed in both normal tissues and tumor cells,while its expression down-regulated in many tumor cell lines, such as Burkitt's lymphoma cell line Daudi.

STGC3 is a novel gene, and down-regulated in NPC and many other tumor cell lines. STGC3 fusion protein distributes in cytoplasm and nucleus.