The effect of a single nucleotide substitution in the splicing silencer in the tat/rev intron on HIV type 1 envelope expression

Abstract

A complex mRNA splicing pattern, which remains to be fully characterized, influences HIV-1 gene expression. In this study, poor envelope expression of a primary HIV-1 isolate was observed and linked to increased splicing of the two coding exons of tat/rev. The substitution of a nucleotide G, located 28 nucleotides upstream of the splice acceptor site SA7 in the recently identified intron splicing silencer sequence, was found to be responsible for the poor envelope expression. A single nucleotide substitution of G with A at this position results in a poor envelope expression phenotype. Moreover, substitution of the nucleotide G with any other nucleotide in an infectious HIV-1 proviral clone, HXB2RU3, results in poor envelope expression. The substitution of this nucleotide reduces the hnRNP A1 binding affinity but increases the splicing of env mRNA. The nucleotide G at this position is highly conserved among HIV-1 isolates and appears to play a critical role in HIV-1 splicing. © Mary Ann Liebert, Inc.