Analysis of Simian Endogenous Retrovirus (SERV) proviruses in Old World Monkey Genomes: Evidence for a Transition to Replication during Embryogenesis

Simian endogenous retrovirus, SERV, is a successful germ line invader restricted to Old World monkey (OWM) species. (1) Background: The availability of high quality primate genomes warrants a study of the characteristics, evolution and distribution of SERV proviruses; (2) Methods: Cercopithecinae OWM genomes from public databases were queried for the presence of full length SERV proviruses. A dataset of 81 Cer-SERV genomes was generated and analyzed; (3) Results: Full length Cer-SERV proviruses were mainly found in terrestrial OWM, and less so in arboreal, forest- dwelling monkeys. Phylogenetic analysis confirmed the existence of two genotypes, Cer-SERV-1 and Cer-SERV-2, with Cer-SERV-1 showing evidence of recent germ line expansions. Long Terminal Repeat (LTR) variation indicated that most proviruses were of a similar age, and were estimated to be between <0.3 and 10 million years old. Integrations shared between species were relatively rare. Sequence analysis further showed extensive CpG methylation-associated mutation, variable Primer Binding Site (PBS) use with Cer-SERV-1 using PBSlys3 and Cer-SERV-2 using PBSlys1,2, and the recent gain of LTR motifs for transcription factors active during embryogenesis in Cer-SERV-1; (4) Conclusions: sequence analysis of 81 SERV proviruses from Cercopithecinae OWM genomes provides evidence for the adaptation of this retrovirus to germ line reproduction.