Specificity of baculovirus p10 functions.

Three functional domains in baculovirus p10 proteins have been postulated for aggregation, nuclear disintegration, and fibrillar structure formation (Van Oers et al., J. Gen. Virol. 74, 563-574, 1993). To study the specificity of these functions, a recombinant Autographa californica nuclear polyhedrosis virus (AcCR1) was constructed in which the coding sequence of the p10 gene was replaced with the p10 sequence of the distantly related Spodoptera exigua (Se) MNPV. In AcCR1-infected cells the SeMNPV p10 protein was produced at similarly high levels as AcMNPV p10 in wild type (wt) AcMNPV infections. Formation of fibrillar structures occurred in a similar fashion in SeMNPV and AcCR1-infected cells. Hence, the SeMNPV p10 protein retained the ability to associate into fibrillar structures when expressed in an otherwise AcMNPV context. Mixed infection with wt AcMNPV and AcCR1 indicated that only p10 proteins of the same species aggregate and that these aggregates associate into fibrillar structures. In contrast to S. exigua cells infected with AcMNPV or SeMNPV, S. exigua cells infected with AcCR1 failed to release polyhedra. This result indicated that interaction of p10 with at least one virus-specific factor is required for nuclear disintegration.