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IE0 and IE1 are transactivator proteins of the most studied baculovirus, the <em>Autographa californica</em> 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 <em>hr5</em> origin of replication of AcMNPV in transient transfections with a battery of eight plasmids expressing the AcMNPV genes <em>dnapol</em>, <em>helicase</em>, <em>lef</em>-1, <em>lef-</em>2, <em>lef</em>-3, <em>p35</em>, <em>ie</em>-2 and <em>lef</em>-7. IE0 transactivated expression of the baculovirus <em>39K</em> 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.