Novel endogenous type C retrovirus in baboons: Complete sequence, providing evidence for baboon endogenous virus gag-pol ancestry

A complete endogenous type C viral genome has been isolated from a baboon g enomic library. The provirus, Papio cynocephalus endogenous retrovirus (PcE V), is 8,572 nucleotides long, and 38 to 59 proviral copies per baboon geno me are found. The PcEV provirus possesses the typical simple retroviral gen e organization, including two long terminal repeats and genes encoding gag, pol, and env proteins. The open reading frames for gag-pol and env are com plete but have premature stop codons or frameshift mutations. The primer bi nding site of PcEV is complementary to tRNA(Gly). The gag and pol genes of PcEV are closely related to those of the baboon endogenous virus (BaEV). Th e env coding region of PcEV is related to the env genes of type C retroviru ses. This suggests that PcEV is one of the ancestors of BaEV contributing t he type C gag-pol genome fragment to the type C/D recombinant virus BaEV. E arlier it was shown that another endogenous type D virus (simian endogenous retrovirus) provided the ear gene for BaEV (A. C. van der Kuyl et al., J. Virol. 71:36663676, 1997).