Involvement of tRNA in retrovirus expression: biological implications of reverse transcriptase-primer tRNA interactions.

We have previously studied the topographical and functional implications of the recognition of primer tRNATrp by avian retrovirus reverse transcriptase. Here we have presented evidence that the enzyme is able to deacylate beef liver Trp-tRNATrp, provided that 35-S viral RNA is present in the incubation mixture. No effect of dNTPs on this activity was observed. The extensive modification of tRNATrp with acrylonitrile led to a marked loss of priming activity by tRNATrp if the annealing between primer and template was performed at 37 degrees C, while the annealing of cyanoethylated tRNA with the viral genome at 75 degrees C gave almost normal levels of cDNA synthesis. We have also studied the priming behaviour of tRNATrp, modified by incorporation of various analogs of adenosine. Only tRNATrp-2'dA was active in cDNA initiation; 3'dA, 3'NH2-3'dA, and primer tRNA with formycin in the 3' end showed low or nonexistent priming activity.