CHARACTERIZATION OF A HUMAN WNT7B GENE AND ITS UP REGULATION IN GASTRIC CANCER CELL LINES
The WNT family of secreted proteins is a group of signaling molecules that control a diverse range of developmental processes including cell proliferation and tumorigenesis. We have constructed a subtracted full-length cDNA library from a human gastric cell line SNU5 using the capping and subtraction method and isolated and characterized the full-length cDNA of human WNT7b. Cloned cDNA sequence comprised 1440 bp including the 5'-noncoding region of 374 bp, an ORF of 1050 bp and the 3'-noncoding region of 16 bp. The ORF could encode a protein of 349 amino acids. Analysis of deduced amino acid sequence showed a conserved WNT signature sequence (CKCHGvSGSC), characteristic 25 cysteine residues and three different N-glycosylation sites at 83, 127, and 295 of asparagines. Comparison of cloned WNT7b with previously reported human WNT7b revealed that cloned WNT7b has 100% identity with nucleotide sequence in coding sequence but has more 279 bp than that in 5'-noncoding region. Also, comparison of cloned WNT7b with mouse WNT7b showed 91% identity in nucleotide sequence and 99% in amino acid sequence. Furthermore, a phylogeny of WNT7b in relation to other known WNT proteins revealed that human WNT7b has a close paralog with other WNT7b proteins across the different species and genus, not with human WNT7a. Besides, expression profiles in different gastric cell lines by RT-PCR showed higher expression of human WNT7b in cancer cell lines than in normal cells, suggesting that human WNT7b has a crucial role in gastric tumorigenesis.
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