COAMPLIFICATION AND DISPERSION OF ADJACENT HUMAN ENDOGENOUS RETROVIRAL HERV-H AND HERV-E ELEMENTS - PRESENCE OF SPLICED HYBRID TRANSCRIPTS IN NORMAL LEUKOCYTES

In an RT-PCR study of HERV-H spliced subgenomic transcripts, we found transcripts with HERV-H leader and protease-encoding sequences spliced to HERV-E integrase-encoding sequences in lymphocytes from healthy bl ood donors. In other cell types, including two T-cell leukemia cell li nes, these transcripts were absent. The PCR fragments of the hybrid tr anscripts contained two open reading frames (ORFs). One was a hybrid H ERV-H protease/HERV-E integrase ORF and the other was the HERV-E envel ope surface glycoprotein ORF. Alternative splice products were also id entified. The genomic DNA origin of the hybrid transcripts was shown t o be a HERV-H element with a large 3'-end deletion, adjacent to a HERV -E element lacking the 5'-LTR. This hybrid structure was shown to be a mplified and dispersed to six different human chromosomes. Thus, a rel atively large part of full-length HERV-E elements(15-20%) is potential ly under the transcriptional control of HERV-H LTRs. The HERV-H/HERV-E junction was present in multiple copies also in the chimpanzee and go rilla, but not in the orangutan or old world monkeys. (C) 1998 Academi c Press.