INTERACTION OF 68-KDA TAR RNA-BINDING PROTEIN AND OTHER CELLULAR PROTEINS WITH PRION PROTEIN-RNA STEM-LOOP

The RNA stem-loop structure of the trans-activating region TAR sequenc e of human immunodeficiency virus-1 mRNA is the binding site for a num ber of host cell proteins. A virtually identical set of proteins from HeLa nuclear extracts was found to bind to the predicted RNA hairpin e lement of prion protein (PrP) mRNA, as demonstrated in UV cross-linkin g/RNase protection and Northwestern assays. We show that the cellular TAR loop-binding protein, p68, is among those proteins which associate with PrP RNA. Competition experiments with various TAR RNA mutants re vealed that binding of partially purified p68 to PrP RNA stem-loop occ urs sequence-specifically. The 100-kDa 2-5A synthetase which is involv ed in the cellular antiviral defense was able to bind to PrP mRNA stem -loop in Northwestern blots with cytosolic proteins from HeLa cells tr eated with interferon, However, the PrP RNA failed to activate this en zyme in vitro, in contrast to TAR RNA.