Specific regulation of mRNA splicing in vitro by a peptide from HIV-1 Rev.

The Rev protein of HIV-1 regulates the synthesis of partially spliced forms of cytoplasmic viral mRNA by binding to a cis-acting RNA sequence, the Rev response element (RRE). We have investigated the regulation of splicing in vitro and have shown that Rev specifically inhibits splicing of pre-mRNAs containing an RRE by 3- to 4-fold. A synthetic peptide of 17 amino acids containing the RNA-binding domain of Rev is highly functional and specifically inhibits splicing by up to 30-fold. Other peptides that bind to the RRE with high affinity, but with low specificity, do not specifically inhibit splicing. Six repeated monomeric binding sites for the peptide can substitute for the RRE, indicating that regulation by Rev requires interactions with multiple sites. The peptide acts at a step in the assembly of splicing complexes, suggesting that one of the functions of the basic region of Rev is to prevent formation of a functional spliceosome.