Oncogene database

2771

GNAI2

guanine nucleotide binding protein (G protein), alpha inhibiting activity polypeptide 2;GNAI2;guanine nucleotide binding protein (G protein), alpha inhibiting activity polypeptide 2

GTP-binding regulatory protein Gi alpha-2 chain|adenylate cyclase-inhibiting G alpha protein|guanine nucleotide-binding protein G(i) subunit alpha-2|guanine nucleotide-binding protein G(i), alpha-2 subunit

3p21.31

protein-coding

The human GNAI2 gene coding for G protein, Galphai2, is located on chromosome 3p21 in proximity to the region where an inflammatory bowel disease (IBD) locus has been suggested. Galphai2-deficient mice develop a lethal diffuse colitis that resembles human ulcerative colitis (UC) and frequently progresses to colon adenocarcinoma. Furthermore, the human GNAI2 gene is subject to point mutations at certain positions, including three at codon 179, ALL of which have been reported in human endocrine tumors. In order to evaluate the possible involvement of this gene in IBD pathogenesis, we have examined GNAI2 codon 179 sequences in 28 familial IBD patients, including 13 UC, 15 Crohn s disease (CD), and 7 patients with colon cancer/dysplasia, from 12 multiplex IBD families. The wildtype codon 179, CGC for arginine, plus the first G of the codon 180 engender a sequence recognizable by the enzyme BstUI. mutations, therefore, can result in the abrogation of BstUI digestion of polymerase chain reaction (PCR) products containing the codon 179. Using the PCR-restriction fragment length polymorphism technique, ALL 28 IBD patients, including those with colon cancer, and 14 non-IBD family members show a BstUI-cleavable PCR-banding pattern indicating the presence of wildtype codon 179. We conclude that, in the familial IBD and colon cancer/dysplasia patients studied, there is no detectable mutation in the codon 179 of the GNAI2 gene.

MicroRNA deregulation is a critical event in tumor initiation and progression. The down-regulation of microRNA-138 has been frequently observed in various cancers, including tongue squamous cell carcinoma (TSCC). Our previous studies suggest that deregulation of miR-138 is associated with the enhanced proliferation and invasion in TSCC cells. Here, we seek to identify the targets of miR-138 in TSCC, and explore their functional relevance in tumorigenesis. Our genome-wide expression profiling experiments identified a panel of 194 unique transcripts that were significantly down-regulated in TSCC cells transfected with miR-138. A comprehensive screening using six different sequence-based microRNA target prediction algorithms revealed that 51 out of these 194 down-regulated transcripts are potential direct targets for miR-138. These targets include: chloride channel, nucleotide-sensitive, 1A (CLNS1A), G protein alpha inhibiting activity polypeptide 2 (GNAI2), solute carrier family 20, member 1 (SLC20A1), eukaryotic translation initiation factor 4E binding protein 1 (EIF4EBP1), and Rho-related GTP-binding protein C (RhoC). GNAI2 is a known proto-oncogene that is involved in the initiation and progression of several different types of tumors. Direct targeting of miR-138 to two candidate binding sequences located in the 3 -untranslated region of GNAI2 mRNA was confirmed using luciferase reporter gene assays. Knockdown of miR-138 in TSCC cells enhanced the expression of GNAI2 at both mRNA and protein levels. In contrast, ectopic transfection of miR-138 reduced the expression of GNAI2, which, in consequence, led to reduced proliferation, cell cycle arrest and apoptosis. In summary, we identified a number of high-confident miR-138 target genes, including proto-oncogene GNAI2, which may play an important role in TSCC initiation and progression.