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Trans-Activation of a Cell Housekeeping Gene Promoter by the IE1 Gene Product of Baculoviruses

1996; Elsevier BV; Volume: 218; Issue: 1 Linguagem: Inglês

10.1006/viro.1996.0170

1096-0341

Maolong Lu, Russell R. Johnson, Kostas Iatrou,

Invertebrate Immune Response Mechanisms

Protein IE1 is the product of a baculovirus gene,ie1,that is activated immediately upon entrance of the viral genome into the cell nucleus. This protein was previously shown to be atrans-regulator of viral genes whose products are required for initiation of the infectious cycle including viral DNA replication. To test whether the IE1 protein is also capable oftrans-regulating nuclear genes of the hostin vitroandin vivo,we transfected theie1gene ofBombyx morinuclear polyhedrosis virus (BmNPV) into silkworm Bm5 tissue culture cells together with expression cassettes directing expression of chloramphenicol acetyl transferase or juvenile hormone esterase under the control of the cytoplasmic actin A3 gene promoter ofB. mori.Cotransfection with theie1gene resulted in a dramatic increase in the amount of the two enzymes expressed in the transfected cells. The increased enzyme activities correlate with an increased accumulation of the corresponding mRNAs, and the latter is caused by an increase in the rate of transcription directed by the cytoplasmic actin gene promoter. The chromosomal cytoplasmic actin gene of Bm5 cells is also upregulated upon transfection of the cells with theie1gene. However, infection of cells with BmNPV does not cause an increase in the level of expression of the endogenous cytoplasmic actin gene. Thus, the effect of IE1 on the transcriptional properties of the cytoplasmic actin gene vary depending on whether IE1 is expressed in isolation or in the context of a viral infection. Thetrans-activating effects of BmNPVie1gene expression on the silkmoth actin promoter are also evident inSpodoptera frugiperdaSf21 andChoristoneura fumiferanaCf1 tissue culture cells. Finally, theie1gene ofAutographa californicanuclear polyhedrosis virus can substitute for its BmNPV counterpart in all cell lines tested.