RNAS SELECTED IN-VITRO BY THE HIV-2 TAT PROTEIN

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 effi cient viral replication. Tat proteins activate viral transcription by binding to the TAR RNA stem-loop structure at the 5' end of viral tran scripts. We used an in vitro selection procedure to identify RNAs pres ent in a large sequence pool that are able to bind to purified Tat-2 p rotein. The sequences of the selected RNAs demonstrated a consensus fe ature: 20 of 27 RNAs contained computer-predicted loop structures that were >50% U or C nucleotides. A selected RNA was characterized for it s in vitro binding properties to various Tat-2 proteins. This syntheti c 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 requ ired a wild-type RNA binding domain to bind to this synthetic RNA. Thi s study indicates that in vitro selection techniques can be used to in vestigate Tat protein-TAR RNA interactions.