HERV-H ENDOGENOUS RETROVIRUSES - PRESENCE IN THE NEW-WORLD BRANCH BUTAMPLIFICATION IN THE OLD-WORLD PRIMATE LINEAGE

The evolutionary origin and age of the HERV-H family of human endogeno us retrovirus-like sequences was investigated in this study. HERV-H el ements exist in approximately 900 partially deleted copies and 50-100 more intact forms in humans and Old World monkeys. However, their poss ible presence in more divergent species is unknown. We have isolated a 1.6-kb genomic DNA segment from the New World monkey marmoset that ha d been PCR amplified using human HERV-H primers. DNA and protein compa risons and database searches indicate that this marmoset clone is more closely related to human HERV-H elements than to any other sequence, indicating that HERV-H-related sequences do exist in New World monkeys . In contrast to the high copy numbers of deleted elements in Old Worl d primates, Southern blot analysis shows that such elements are presen t in less than 50 copies in two different species of New World monkey. To estimate evolutionary ages of the common deleted form of the eleme nt, a selected DNA segment from the pol region was compared from multi ple human HERV-H elements. This comparison suggests that many HERV-H e lements of the abundant deleted subfamily integrated approximately 30- 35 million years ago. Very similar percentage divergence values betwee n 5' and 3' long terminal repeats of individual elements of the delete d subfamily also suggest that these elements are close in age. These r esults indicate that HERV-H elements first appeared in the germline pr ior to the New World/Old World divergence over 40 million years ago. I nterestingly, they remained in low numbers in the New World branch whi le a subfamily underwent a major amplification in Old World primates b efore the time of divergence of hominoids from Old World monkeys. (C) 1995 Academic Press, Inc.