Dynamic nuclear localization of the baculovirus proteins IE2 and PE38 during the infection cycle: the promyelocytic leukemia protein colocalizes with IE2.
ABSTRACT The early gene products IE2 and PE38 of Autographa californica multicapsid nuclear polyhedrosis virus localize to distinct nuclear domains after transient expression. Here, the nuclear localization pattern and the putative association with cellular proteins have been determined during virus infection to shed light on the functional significance of the nuclear domains. IE2 was always localized to distinct nuclear structures while PE38 was partly present in nuclear dots. Confocal imaging indicated colocalization of PE38 and IE2 to common domains, prominently at 2 h p.i. The nuclear dot localization of PE38 in infected cells was different from that in transfected cells. Hence, we have performed cotransfection experiments that suggested that a viral factor influences the nuclear distribution. Since the promyelocytic leukemia protein (PML) that localizes to distinct nuclear multiprotein complexes termed ND10/PODs in mammalian cells functions as a target for some immediate early viral proteins, we have investigated whether baculovirus proteins act similarly. Transiently expressed IE2 and PE38 were found to be associated with endogenous PML in the mammalian cell line BHK21. Infection with a recombinant virus that expresses the human pml gene in insect cells reveals IE2 and PML to be colocalized during the early phase of infection followed by a redistribution of both proteins. Taken together our results provide first evidence that the early baculovirus protein IE2 associates at least with one component of mammalian PODs during virus infection, suggesting that POD-like structures can be formed in insect cells.
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ABSTRACT: To follow the progression of infection of Autographa californica multicapsid nuclear polyhedrosis virus (AcMNPV) within tissues of its larval host, we have constructed AcMNPV recombinants carrying lacZ reporter genes under the control of the early virus promoters pe38 and me53, in addition to the authentic genes. The early promoter-lacZ gene cassettes were located upstream of the very late polyhedrin gene. In infected insect cell lines, pe38 transcription is initiated at an early promoter, while me53 transcripts start from both early and late sites. Transcriptional mapping of the duplicated me53 and pe38 promoters driving lacZ expression showed that they initiated at the same start sites as in the authentic genes. Expression of lacZ by these recombinants was compared to a recombinant driving beta-glucuronidase expression from the very late p10 promoter and lacZ expression from the constitutive heat shock protein 70 promoter of Drosophila melanogaster. After infection of Spodoptera exigua larvae with the different recombinants, we followed reporter gene expression and polyhedron formation in different tissues using immunohistochemistry and electron microscopy. LacZ expression, indicative of early viral transcriptional activity, was detected in nearly all larval tissues during the course of infection. In most tissues these early events were followed by pathophysiological changes associated with late and very late gene expression. However, p10 transcription and polyhedron formation were not observed in midgut goblet cells, Malpighian tubules and salivary glands. These results suggest that expression of early virus genes, such as me53 and pe38, is not restricted to larval tissues that are permissive for AcMNPV replication.Journal of General Virology 06/1996; 77 ( Pt 5):815-24. · 3.13 Impact Factor
- The American Journal of Human Genetics 09/1998; 63(2):297-304. · 11.20 Impact Factor
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ABSTRACT: Trans-acting regulatory components of Autographa californica nuclear polyhedrosis virus (AcMNPV) were studied in a transient assay system for their ability to activate the p143 gene promoter. A region including 502 nt upstream of the AUG of the p143 gene was linked to the bacterial chloramphenicol acetyltransferase (CAT) gene. The p143 promoter-CAT construct was used to identify AcMNPV immediate-early gene products required for expression from the p143 gene early promoter. Transient expression assays in uninfected Spodoptera frugiperda cells indicated that the IE-1 gene product was capable of transactivating the p143 gene promoter and this activation was augmented by the IE-N gene product. In addition, another immediate-early gene, PE-38, was shown to mediate transactivation of the p143 gene promoter but not the 39K delayed early gene promoter. Deletions to -187 bp relative to the p143 RNA start site did not significantly affect promoter activity in the combined presence of IE-1 and the HindIII-F fragment. However, a deletion to -52 bp decreased promoter activity by 40%. In contrast, in the presence of ts8 DNA at 33 degrees, deletions to -52 bp decreased promoter activity by 80% suggesting that additional viral factors were involved in p143 gene promoter regulation.Virology 09/1993; 195(2):710-8. · 3.37 Impact Factor