Adenovirus-induced inhibition of cellular DNase

During the productive infection of KB cells by adenovirus type 5 (Ad5), there is a progressive decrease in the level of cellular DNase activity towards single-stranded DNA, in contrast to DNA polymerase which remains relatively constant throughout the infection. This decrease is prevented by the inhibition of protein synthesis by cycloheximide. The inhibition of DNase activity does not occur after infection by Ad5 ts125, a DNA-negative mutant which fails to induce the adenovirus-specific DNA binding protein. In contrast, infection by Ad5 ts36, a DNA-negative mutant which complements ts125, does result in decreased levels of DNase. A mechanism is discussed in which the DNA binding protein protects viral replicative intermediates from degradation by cellular DNase.