Viral DNA and a viral peptide can act as cofactors of adenovirus virion proteinase activity

Abstract

HUMAN adenovirus (Ad2), like many other viruses¹, contains a virion-associated proteinase essential for the synthesis of infectious virus particles^2–4. 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 recombinant^6,7 endoprotease protein (M_r 23 K). Purified recombinant endo-protease 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.