Functional Cloning And Characterization Of Human Novel Gene PP3105

Hepatocellular carcinoma (HCC), the highly prevalent human cancer in the world, is one of the major death causes of malignant diseases in China. In our country, the rate of new suffering resides the third of the female and the fourth of the male respectively. As a whole, the prognosis after treatment is extremely poor as compared to most other cancers. The fundamental obstacles are too little knowledge we have concerning the mechanism of hepatocarcinogensis and progression of HCC, especially the molecular basis of these processes. Human malignant tumors often unmask cumulative genetic changes which include the activation of oncogenes and the inactivation of tumor-suppressor genes during development and progression.In order to obtain novel genes related to liver cancer, our laboratory has established a high-throughput, cell growth-based functional screening method. Using this high-throughput method we screened a human placenta cDNA library of fragments bigger than 2kb, picked up the clones having remarkable influence on proliferation, differentiation and apoptosis of cancer cells, carried out sequencing, and cloned the full length of novel genes by RACE. PP3105 is the novel cDNA isolated by our laboratory that could influence the proliferation of the cancer cells. Using BLAST program in NCBI website and calculate electronic cloning, we got two different transcripts named PP3105-A and PP3105-B. PP3105-A is as same as the cDNA of GenBank No. NM 022154. The full-length PP3105-A and PP3105-B encode 460 and 246 amino acids respectively. The result of Northern blotting indicates that PP3105 displays a high level of expression in heart, placenta, lung, liver, kidney and pancreases. The two transcripts have different expression in structure of human. The biological informatics show that PP3105 have N-glycosylation site, Protein kinas C phosphorylation site, Casein kinas II phosphorylation site, N-myristoylation site, Amidation site and Leucine zipper pattern, may be a zinc transporter. Through Radiation Hybrid mapping, PP3105 was assigned to chromosome 4q22-24.Colony formation, sub cellular localization, and proliferation curve experiments were used to study its function, Sub cellular localization showed that PP3105 is a novel membrane-associated protein. In the colony formation experiments, PP3105 suppressed the colony formation efficiency of transfected SMMC7721. MTS assay of the SMMC7721 transfected with this gene showed its inhibiting role to cellularproliferation. So we presume that PP3105 may be a zinc transporter and involved in hepatocellular carcinoma development.