DNA-binding proteins of baculovirus-infected cells during permissive and semipermissive replication

Certain insect cell lines have been shown to be permissive (TN-368) or semipermissive (IPLB-LD-652Y) for Autographa califomica nuclear polyhedrosis virus (AcMNPV) replication (McClintock et al., 1986b). In this report DNA-binding proteins were identified in such cell:virus systems by hybridizing Western blots containing uninfected and infected cell proteins with AcMNPV or host DNA probes. In the AcMNPV-infected TN-368 permissive cell system, 8 virus-induced DNA-binding proteins with molecular weights ranging from 67.5K to 18.75K were observed under the highest conditions of stringency. When these DNA-binding proteins were compared to structural proteins of AcMNPV, several appeared to be similar to those observed in SDS-PAGE protein profiles of nonoccluded virus (NOV) and occlusion body (PIBs) preparations. Using an AcMNPV occlusion negative mutant (L1GP- gal3) and an anti-AcMNPV-polyhedrin monoclonal antibody, a major DNA-binding protein (33.0K), observed in the permissive system, corresponded to polyhedrin and to a comigrating virus-induced DNA-binding protein. In the AcMNPV-infected IPLB-LD-652Y semipermissive cell system, no virus-induced DNA-binding proteins were detected. However, several host DNA-binding proteins were present but their ability to bind DNA decreased significantly following infection.