Stem loops in HIV and prion protein mRNAs.

Tat-dependent trans-activation in HIV requires presentation of a CUGGG pentanucleotide at the end of a stem loop within the tar site of the viral long terminal repeat. A tandem repeat within the open reading frame of the prion protein (PrP) mRNA is able to form similar stem loop structures with which the HIV tat protein could interact, disturbing PrP translation. Self-amplification of such a disturbance has been suggested as the cause of the scrapie group of diseases, including the scrapie-like human dementiae. The same mechanism may underly AIDS encephalopathy.