Identification of unusual and novel HIV type 1 spliced transcripts generated in vivo

HIV-1 transcripts are generated through a complex alternative splicing mechanism, resulting in the production of multiple RNAs coding for each viral protein. HIV-1 RNA splicing has been analyzed mostly in in vitro assays, and in vivo data are scarce. Here we analyze HIV-1 transcripts generated in peripheral blood mononuclear cells of HIV-1-infected individuals by RT-PCR amplification and sequencing of RNA extracted from unstimulated cells. We identify several unusual or unreported transcripts, most of them splicing within the Nef coding sequence. The majority are predicted to code for a Nef C-terminal 34 amino acid peptide, but others code for Vpr, a truncated Tat, and a 41 amino acid peptide encoded in an antisense exon. We also identify nef and env transcripts splicing four nucleotides downstream of SA5. These results represent the first report on the in vivo generation of diverse novel HIV-1-spliced transcripts, frequently encoding a Nef C-terminal peptide.