Abstract
IE0 and IE1 are transactivator proteins of the most studied baculovirus, the Autographa californica multiple nucleopolyhedrovirus (AcMNPV). IE0 is a 72.6 kDa protein identical to IE1 with the exception of its 54 N-terminal amino acid residues. To gain some insight about important structural motifs of IE0, we expressed the protein and C‑terminal mutants of it under the control of the Drosophila heat shock promoter and studied the transactivation and replication functions of the transiently expressed proteins. IE0 was able to promote replication of a plasmid bearing the hr5 origin of replication of AcMNPV in transient transfections with a battery of eight plasmids expressing the AcMNPV genes dnapol, helicase, lef-1, lef-2, lef-3, p35, ie-2 and lef-7. IE0 transactivated expression of the baculovirus 39K promoter. Both functions of replication and transactivation were lost after introduction of selected mutations at the basic domain II and helix-loop-helix conserved structural motifs in the C-terminus of the protein. These IE0 mutants were unable to translocate to the cell nucleus. Our results point out the important role of some structural conserved motifs to the proper functioning of IE0.
Highlights
IE0 and IE1, are transactivator proteins of the most studied baculovirus, the Autographa californica multiple nucleopolyhedrovirus (AcMNPV)
N-terminus, separated by the basic domain I (BDI) which is required for binding to hrs, enhancer elements of the AcMNPV genome that function as origins of DNA replication [11,14,15,16] and reviewed in [17]
It follows that understanding the function of IE0 may help to elucidate the regulation of AcMNPV infections in permissive and non permissive cells and in this study we took a first step in this direction
Summary
IE0 and IE1, are transactivator proteins of the most studied baculovirus, the Autographa californica multiple nucleopolyhedrovirus (AcMNPV). IE1 was reported to down regulate the expression of ie0 we decided to directly test the function of IE0 in an IE1-free transient assay in this study (see below). From the above, it follows that understanding the function of IE0 may help to elucidate the regulation of AcMNPV infections in permissive and non permissive cells and in this study we took a first step in this direction. To gain some insight about important structural motifs for the functions of IE0 in an IE1-free environment, we expressed the protein and C-terminal mutants of it under the control of the Drosophila heat shock promoter and studied the transactivation and replication functions of the transiently expressed proteins
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