The Autographa californica multiple nucleopolyhedrovirus (AcMNPV) protein p74 is associated with the occlusion-derived virus (ODV) envelope. p74 is essential for oral infectivity of ODV and has been proposed to play a role in midgut attachment and/or fusion. In this study, p74 protein was expressed in-frame with green fluorescent protein (GFP) to create a p74-GFP chimera. The Cterminal GFP portion of the chimera facilitated visualization of the trafficking of p74 in baculovirusinfected Spodoptera frugiperda (Sf-9) cells. p74-GFP chimeric proteins localized in the intranuclear ring zone of the nucleus and were found to co-precipitate with the microvesicle fraction of cell lysates. A series of truncations of p74 was expressed as p74-GFP chimeras in recombinant baculoviruses. When C-terminal region S580-F645 was deleted from p74, p74-GFP chimera localization became non-specific and chimeras became soluble. p74 region S580-F645 directed GFP to the intranuclear ring zone in a similar pattern to full-length p74. The hydrophobic C terminus of p74 plays a role in protein localization and possibly in transmembrane anchoring and insertion.

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Infection of two gypsy moth cell lines (IPLB-Ld652Y and IPLB-LdFB) by the Autographa californica multiple-enveloped nuclear polyhedrosis virus (AcMNPV) is characterized by extremely attenuated viral protein synthesis followed by a total arrest of all viral and cellular protein production. In this study, AcMNPVand host cell-specific transcription were examined. Overall levels of viral RNAs in infected gypsy moth cells were, at most measured times, comparable to RNA levels from an infected cell line (TN-368) permissive for AcMNPV replication. Northern blot (RNA) analyses using viral and host gene-specific probes revealed predominantly normal-length virus-and cell-specific transcripts postinfection. Transport of viral RNAs from the nucleus to the cytoplasm and transcript stability in infected gypsy moth cells also appeared normal compared with similar parameters for AcMNPV-infected TN-368 cells. Host cellular and viral mRNAs extracted from gypsy moth and TN-368 cells at various times postinfection and translated in vitro yielded similar spectra of host and viral proteins. Treatment of infected gypsy moth cells with the DNA synthesis inhibitor aphidicolin eliminated the total protein synthesis shutoff in infected IPLB-LdFB cells but had no effect on protein synthesis inhibition in infected IPLB-Ld652Y cells. The apparent selective block in the translation of viral transcripts early in infection and the absence of normal translation or transcription of host cellular genes at later times is discussed.