Allosteric Inhibition of the HIV-1 Rev/RRE Interaction by a 3′-Methylphosphonate Modified Antisense Oligo-2′-O-Methylribonucleotide

Abstract

The HIV-1 Rev response element (RRE), a highly structured RNA sequence consisting of five stemloops, is found in all spliced and partially spliced human immunodeficiency virus (HIV) mRNA transcripts. The RRE interacts with HIV-encoded Rev protein, which facilitates exit of the transcripts from the nucleus to the cytoplasm. Because the Rev/RRE interaction is critical to virus function, it is considered a potential target for therapeutic drugs. We have investigated the interactions of antisense oligonucleotides with stem-loop II, a region that contains the high-affinity binding site for Rev. Oligo-2'-O-methylribonucleotides terminating in a nuclease resistant 3'-methylphosphonate internucleotide linkage were targeted to the 5'- or 3'-side of stem-loop IIB, which is adjacent to the Rev binding site. Thermal denaturation experiments showed that oligonucleotides of this type form highly stable duplexes with complementary single-stranded RNA. Gel electrophoretic mobility shift assays (EMSA) showed that the oligonucleotides bound with high affinity and specificity at 37 degrees C to RRE stem-loop II RNA with apparent dissociation constants, K(D), in the low nM range. A 16-mer, 2-1mp, whose K(D) is 46 nM, competitively inhibited binding of Rev peptide to RRE stem-loop II RNA as shown by EMSA experiments. When transfected into HEK 293T cells, 2-1mp inhibited RRE mediated expression of chloramphenicol acetyl transferase (CAT) by 60% at a concentration of 300 nM oligonucleotide. These results are consistent with a mechanism by which 2-1mp blocks access of Rev to the RRE/CAT transcript thus preventing nuclear export and subsequent translation.