NMR ANALYSIS OF THE TRANSACTIVATION RESPONSE (TAR) RNA ELEMENT OF EQUINE INFECTIOUS-ANEMIA VIRUS

Transcription of lentiviral DNA in the host cell is regulated by an in teraction between the viral TAR RNA stem-loop and the viral Tat protei n. Here we present a model of the three-dimensional structure of the T AR RNA stem-loop of the equine infectious anemia virus (EIAV), derived from two- and three-dimensional NMR data. This 25 nucleotide RNA cons ists of an A-form helical stem capped by two U-G base pairs and a four -nucleotide loop. Two loop cytidines are stacked into the loop interio r and likely form a non-Watson-Crick C-C base-pair. The two nucleotide s at the top of the loop, U13 and G14, appear to be excluded from the interior of the loop and solvent exposed. It is significant that now f or the EIAV TAR-Tat system, three-dimensional structures are now known for both the RNA and protein components.