Expression and phylogenetic analyses of human endogenous retrovirus HC2 belonging to the HERV-T family in human tissues and cancer cells.

Recently, a new HERV-T family, representative of the HERV-S71 and HERV-HC2 family, was identified using a screen for envelope genes and a computer-assisted database search. Here, we investigate expression of pol fragments of HERV-HC2 belonging to the HERV-T family in various human tissues and cancer cells. The pol gene was expressed in nearly all human tissues examined and in all cancer cell lines. Expression analyses suggest that the pol gene of HERV-HC2 family is more actively transcribed in human cancer cells than in normal tissues, suggesting a functional role during carcinogenesis. Phylogenetic analysis of the HERV-HC2 pol family revealed three groups (I, II, and III) generated through evolutionary divergence during primate evolution, indicating that they were integrated into primate genomes approximately 56 million years (MY) ago and have evolved at a rate of 0.2% nucleotide differences per MY. Our data might contribute to an understanding of the information on the transcriptional and pathological potential of the HERV-T family in human disease, including cancer.