Characterization of adenovirus-associated virus-induced polypeptides in KB cells.

Electrophoretic analysis of KB cells coinfected with adenovirus-associated virus (AAV) type 2, a defective parvovirus, and adenovirus type 5 (as helper) have revealed the synthesis in vivo of at least five AAV-specific polypeptides. The three largest polypeptides, with molecular weights of 90,700, 71,600, and 60,000 comigrated in polyacrylamide gels with the three AAV structural polypeptides. The remaining two polypeptides had molecular weights of 24,900 and 15,800. The concentrations of the AAV-induced polypeptides relative to one another remained approximately constant during the infectious cycle, and the structural components were present in proportions similar to those found in purified virions. As determined by pulse-chase experiments, all polypeptides were generated at the level of protein synthesis and not by posttranslational proteolytic processing. Although inhibitors of proteolytic enzymes failed to influence the pattern of AAV-induced polypeptides, and amino acid analog, L-canavanine, blocked the appearances of both the major structural polypeptide (60,000 daltons) and the larger nonstructural polypeptide (24,900 daltons). Taken in conjunction with pulse-chase data, this result supports a model whereby the major virion polypeptide is produced by proteolytic cleavage of the nascent polypeptide chain.