The Trichoplusia ni granulovirus helicase is unable to support replicationof Autographa californica multicapsid nucleopolyhedrovirus in cells and larvae of T-ni

Baculovirus DNA helicases are essential for replication and are determinant s of host range. Helicases of Autographa californica multicapsid nucleopoly hedrovirus (AcMNPV) and Trichoplusia ni granulovirus (TnGV) differ markedly , although both viruses replicate efficiently in the cabbage looper, T. ni. To determine whether the TnGV helicase (P137) could support replication of AcMNPV in T. ni cells or larvae, the native AcMNPV helicase gene (p143) wa s disrupted and substituted with p137. P137 did not support replication whe n synthesized by the P143-deficient AcMNPV. Moreover, P137 did not inhibit AcMNPV replication when co-synthesized in the presence of the AcMNPV P143. These results suggest that although TnGV and AcMNPV replicate efficiently i n T. ni, specific protein-protein or protein-DNA interactions between bacul oviral helicases and viral-specific factors which form the replicase comple x are required for virus replication. A novel and rapid method for disrupti ng AcMNPV genes in E. coli using the commercial Bac-to-Bac AcMNPV baculovir us expression vector is described.