Characterization of human TMEM16G gene in silico.

Abstract

TMEM16A, TMEM16B, TMEM16C, TMEM16D, TMEM16E, TMEM16F and TP53I5 are TMEM16 family eight-transmembrane proteins with N- and C-terminal tails facing the cytoplasm. TMEM16A gene at human chromosome 11q13.3 is amplified in head and neck tumors, and TMEM16E gene at human chromosome 11p14.3 is mutated in gnathodiaphyseal dysplasia (GDD). Ngep cDNA (NM_207031.1) is derived from mouse Tmem16g gene. Here, we characterized human TMEM16G gene by using bioinformatics. TMEM16G gene, consisting of 25 exons, was located at human chromosome 2q37.3. Intra-species comparative genomics revealed that the PASK-PPP1R7-TMEM16G-HDLBP-NEDD5 locus was the unique region without paralogous region. TMEM16G mRNA was preferentially expressed in normal prostate and prostate cancer. Complete coding sequence of TMEM16G cDNA was determined by assembling 25 exons of TMEM16G gene. Human TMEM16G gene was found to encode 932-amino-acid TMEM16G protein with TM16H1, TM16H2 and TM16H3 domains. Comparative proteomics revealed that T844N amino-acid substitution occurred in human TMEM16G during evolution. TMHMM2 program predicted that mouse Tmem16g and artificial human TMEM16G (844T) were eight-transmembrane proteins, but that wild-type human TMEM16G (844N) was a seven-transmembrane protein. These facts indicate that amino-acid substitution at codon 844 of human TMEM16G resulted in the mis-folding of the eighth transmembrane helix. Human TMEM16G with altered membrane topology might show functional divergence compared with other members of the TMEM16 family.