Dual roles for the telomeric repeats in chromosomally integrated human herpesvirus-6

Approximately 1 percent of healthy individuals carry human herpesvirus-6 within a host chromosome. This is referred to as chromosomally integrated herpesvirus-6 (CIHHV-6). In this study, we investigated the chromosomal integration site in six individuals harboring CIHHV-6B. Using FISH, we found that HHV-6B signals are consistently located at the telomeric region. The proximal endpoints of the integrated virus were mapped at one of two telomere-repeat-like sequences (TRSs) within the DR-R in all cases. In two cases, we isolated junction fragments between the viral TRS and human telomere repeats. The distal endpoints were mapped at the distal TRS in all cases. The size of the distal TRS was found to be ~5 kb which is sufficient to fulfill cellular telomeric functions. We conclude that the viral TRS in the DR regions fulfill dual functions for CIHHV-6: homology-mediated integration into the telomeric region of the chromosome and neo-telomere formation that is then stably transmitted.