Expression and location of a baculovirus DNA-binding protein within the host cell

Abstract

Antiserum prepared against the basic DNA-binding protein (6.9K) of Autographa californica nuclear polyhedrosis virus (Ac MNPV) was used to follow the time course and localization of this protein within the infected host cell. Using indirect fluorescent antibody assays, the basic protein of the input virus was detectable at early times postinfection (pi). A dramatic increase in the intensity of fluorescence was observed by 15 hr pi and remained at a very high level throughout the time course examined (48 hr pi). The 6.9K protein was detectable at the ultrastructural level using gold-conjugated protein A by 12 hr pi. This correlates well with the timing of the transcript for this protein, the appearance of the 6.9K protein in infected cell lysates resolved in denaturing polyacrylamide gels, and the fluorescent antibody studies. At 12 hr pi the 6.9K was distributed throughout the cytoplasm and nucleus; but by 24 hr following infection, very few gold particles were observed in the cytoplasm. The nuclear localized 6.9K was observed associated with virions and anti-6.9K antibodies were capable of binding to this protein prior to and following occlusion. Gold label was not found on fibrous structures or associated with polyhedrin within the infected nuclei.