RNAs selected in vitro by the HIV-2 tat protein

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Abstract
The Tat proteins of human immunodeficiency virus types 1 (HIV-1) and 2 (HIV-2), termed Tat-1 and Tat-2, respectively, are essential for efficient viral replication. Tat proteins activate viral transcription by binding to the TAR RNA stem-loop structure at the 5' end of viral transcripts. We used an in vitro selection procedure to identify RNAs present in a large sequence pool that are able to bind to purified Tat-2 protein. The sequences of the selected RNAs demonstrated a consensus feature: 20 of 27 RNAs contained computer-predicted loop structures that were >50% U or C nucleotides. A selected RNA was characterized for its in vitro binding properties to various Tat-2 proteins. This synthetic RNA was bound by wild-type Tat-2 proteins with an affinity that was only slightly lower than that of the natural HIV-2 TAR RNA. Tat-2 required a wild-type RNA binding domain to bind to this synthetic RNA. This study indicates that in vitro selection techniques can be used to investigate Tat protein-TAR RNA interactions. Copyright 1997 S. Karger AG, Basel