Photochemical cross-linking of reovirus genome RNA in situ and inactivation of viral transcriptase.

Reovirus infectivity and core-associated RNA polymerase activity were decreased by irradiation with long wavelength ultraviolet light in the presence of the 4'-substituted psoralen derivatives, 4'-aminomethyl-4,5',8-trimethylpsoralen and 4'-hydroxymethyl-4,5',8-trimethylpsoralen. Monoadduct formation occurred after photoreaction with low psoralen concentrations or brief irradiation times, and the presence of KCl or magnesium acetate had a protective effect. Under the mild reaction conditions in which 1 molecule of 4'-aminomethyl-4,5',8-trimethylpsoralen was bound covalently per 160 to 290 base-pairs, the polymerase activity was decreased by greater than 90%. At higher drug concentrations or longer times of photoreaction of reovirus cores, the viral RNA was extensively cross-linked indicating that the reovirus genome in situ is double-stranded.