Genome structure and expression of the ev J family of avian endogenous viruses

We recently reported the identification of sequences in the chicken genome that show over 95% identity to the novel envelope gene of the subgroup J av ian leukosis virus (S. J. Benson, B. L. Ruis, A. M. Fadly, and K. F. Conkli n, J. Virol. 72:10157-10164, 1998). Based on the fact that the endogenous s ubgroup J-related env genes were associated with long terminal repeats (LTR s), we concluded that these LTR-env sequences defined a new family of avian endogenous viruses that we designated the ev/J family. In this report, we have further characterized the content and expression of the ev/J proviruse s. The data obtained indicate that there are between 6 and 11 copies of ev/ J proviruses in all chicken cells examined and that these proviruses fall i nto six classes. Of the 18 proviruses examined, all share a high degree of sequence identity and all contain an internal deletion that removes all of the pal gene and various amounts of gag and env gene sequences. Sequencing of the gag genes, LTRs, and untranslated regions of several ev/J proviruses revealed a high level of identity between isolates, indicating that they h ave not undergone significant sequence variation since their introduction i nto the avian germ line. Although the ev/J gag gene showed a relatively wea k relationship (46% identity and 61% similarity at the amino acid level) to that of the avian leukosis-sarcoma virus family, it retains several sequen ces of demonstrated importance for virus assembly, budding, and/or infectiv ity. Finally, evidence was obtained that at least some members of the ev/J family are expressed and, if translated, could encode Gag- and Env-related polypeptides.