ABSTRACT
Previous reports indicate that mutations within theAutographa californica nucleopolyhedrosis virusFP25K gene (open reading frame 61) significantly reduce incorporation of enveloped nucleocapsids into viral occlusions. We report that FP25K is a nucleocapsid protein of both the budded virus (BV) and occluded virus (ODV), and we describe the effects of twoFP25K mutations (480-1 [N-terminal truncation] and FP-βgal [C-terminal fusion]) on the expression and cellular localization of ODV-E66 and ODV-E25. Significantly decreased amounts of ODV-E66 are detected in cells infected with 480-1 or FP-βgal viral mutants, even though during FP-βgal infection, steady-state levels of ODV-E66 transcripts remain unchanged. While ODV-E66 is normally detected in intranuclear microvesicles and ODV envelopes by 24 h postinfection (p.i.), ODV-E66 remains cytosolic throughout infection in cells infected with 480-1 virus (up to 96 h p.i.), and its intranuclear localization is not detected until 96 h p.i. in cells infected with the FP-βgal mutant virus. The nuclear localization of ODV-E25 is not affected during infection by the FP-βgal mutant; however, its trafficking is significantly delayed during infection by the 480-1 mutant. Temporal Western blot analyses of cell lysates show that both 480-1 and FP-βgal mutant virus infections result in altered accumulation patterns of several structural proteins, including gp67, BV/ODV-E26, and the major capsid protein p39. In addition to BV/ODV-E26, ODV-E66 and gp67 may interact with FP25K, and ODV-E25 and p39 may also be components of a protein complex containing ODV-E66 and FP25K. Together, these data suggest that FP25K and its associated protein complex(es) may play an important role in the targeting and intracellular transport of viral proteins during infection.