Natural antisense transcripts are detected in different cell lines and tissues of cats infected with feline immunodeficiency virus

Feline immunodeficiency virus (FIV) is a lentivirus inducing an AIDS-like d isease in cats, thus providing an interesting model for AIDS study. FIV and HIV-1 possess a similar genomic arrangement of structural and non-structur al genes, whose expression is regulated by related genetic mechanisms. On t he DNA strand complementary to the HIV-1 envelope messenger, an open readin g frame (ORF) has been identified which encompasses the Rev Responsive Elem ent (RRE), a cis-acting element critical to HIV gene expression. This ORF w as highly conserved among HIV-1 isolates and had the potential to encode a hydrophobic protein. A corresponding antisense transcript was detected in c ells infected with HIV-1, and appeared to encode an antisense protein. In t he present study, we have identified a well-conserved antisense ORF, also c oincident with the RRE region, in the genome of 21 FIV isolates. The predic ted protein, 103 amino acids in length, is highly hydrophobic, as is the ca se for that of HIV-1. In addition, we have shown that a corresponding trans cript, complementary to the transmembrane sequence of the Fl[V envelope gen e, was produced in different cellular and viral contexts, that is, ex vivo and in vivo in FIV infected cell lines and tissues of infected cats, respec tively. Expression of antisense transcripts might therefore be of general i mportance in the natural history of retroviruses. (C) 2001 Elsevier Science B.V. All rights reserved.