VIRAL-DNA AND A VIRAL PEPTIDE CAN ACT AS COFACTORS OF ADENOVIRUS VIRION PROTEINASE ACTIVITY

HUMAN adenovirus (Ad2), like many other viruses1, contains a virion-associated proteinase essential for the synthesis of infectious virus particles2-4. We observed proteinase activity in wild-type virus but not in the ts-1 virus2, which contains a mutation in the Ad2 L3 endoprotease gene5 that confers temperature-sensitive processing of virion precursor proteins. Unexpectedly, we did not observe proteinase activity with purified recombinant6,7 endoprotease protein (M(r) 23 K). Purified recombinant endoprotease protein, however, complemented the mutation in ts-1 virions, restoring proteinase activity when mixed together. This implied that cofactors may be required. Here we reconstitute proteinase activity in vitro with three purified viral components: (1) the recombinant endoprotease protein; (2) an 11-amino-acid peptide that originates from the carboxy terminus of pVI, the precursor to virion component VI; and (3) adenovirus DNA. The use of DNA for a proteinase activity is unprecedented.