Chromosomal assignment of human endogenous retrovirus K (HERV-K) env open reading frames

The haploid human genome contains at least one human endogenous retrovirus K (HERV-K) env gene displaying an open reading frame, as evidenced by the high antibody titers against HERV-K Env in germ cell tumor patients at the time of tumor detection. However, the chromosomal assignment of an intact HERV-K env sequence is complicated by the existence of 25-30 HERV-K copies per haploid human genome. Recently, we reported the application of the protein truncation test (PTT) to chromosomally assign HERV-K gag open reading frames. Here, we set out to determine the chromosomal distribution of full-length HERV-K env genes. As demonstrated by somatic hybrid mapping and the PTT, HERV-K env open reading frames were found on human chromosomes 7, 19, and Y. By sequencing chromosome-specific HERV-K env subregions, we assigned two recently reported intact HERV-K sequences on human chromosomes 7 and 19, respectively. Chromosomes 7 and 19 and the Y are furthermore candidates for harboring a putative completely intact HERV-K locus.