FUNCTIONAL DISSECTION OF THE IE2 GENE-PRODUCT OF THE BACULOVIRUS AUTOGRAPHA-CALIFORNICA NUCLEAR POLYHEDROSIS-VIRUS

The Pstl-N genomic fragment of Autographa californica nuclear polyhedr osis virus (AcNPV) encodes an immediate-early protein, IE2, that funct ions as a promiscuous transactivator of other early viral promoters an d heterologous promoters both in vivo and in vitro. IE2 contains sever al sequence motifs that are common to transcriptional activators. We h ave employed site-directed mutagenesis coupled with transient-expressi on assays to identify the amino acid sequences of IE2 that are essenti al for transactivation. Sequential deletion of amino-terminal sequence s of IE2 gradually decreased the activity of the protein. Carboxy-term inal truncations of IE2 resulted in a dramatic loss of transactivation activities. Analysis of IE2 internal-deletion mutants demonstrated th at the acidic amino acid-rich region between amino acids 198 and 206 p ossessed significant transactivation potential for all target promoter s tested. In addition, squelching phenomena exhibited by wild-type IE2 and IE2 deletions containing the acidic amino acid-rich region indire ctly demonstrated that this region may be involved in interactions wit h factors of the basic transcription machinery. (C) 1994 Academic Pres s, Inc.