The chromosomal organization of the human endogenous retrovirus-like sequence HERV-H: clustering of the HERV-H sequences in a 300-kb region close to the GRPR locus on the X chromosome.

Within the haploid genome there are approximately 1,000 copies of the human endogenous retrovirus-like sequence, HERV-H. Although these sequences are scattered throughout the entire genome, in situ hybridization experiments revealed that there are discrete clusters positioned on chromosomes 1 p and 7 q. In this study, we have located three HERV-H sequences which were unexpectedly clustered within a 300-kilobase region close to the GRPR locus on the X chromosome. In previous studies, no clustering of this sequence has been reported at this locus. Our finding demonstrates that, like other repetitive sequences, clustering of HERV-H occurs in the human genome, although these sequences may not always be detected by in situ hybridization methods.