18 BACULOVIRUS GENES, INCLUDING LEF-11, P35, 39K AND P47, SUPPORT LATE GENE-EXPRESSION

We report the identification of four additional genes of the Autograph a californica nuclear polyhedrosis virus involved in expression from a late baculovirus promoter in transient expression assays, Three of th ese genes, p35, 39K, and p47, have been previously described. The role of the p35 gene product in late gene expression may be related to its ability to block apoptosis, since two other baculovirus genes also kn own to block apoptosis, Cp-iap and Op-iap, were able to functionally r eplace p35 in the transient expression assay. The requirement for p47 in this assay confirms its role in late gene expression, a role previo usly established by characterization of a temperature-sensitive mutant of p47, while the requirement for 39K may be related to its known ass ociation with the virogenic stroma, The fourth gene identified as a la te expression factor gene, lef-11, was located immediately upstream of 39K and is predicted to encode a 13-kDa polypeptide. When plasmids co ntaining these 4 genes were cotransfected with plasmids containing the 14 genes previously identified as late gene expression factors, the l evel of expression from the late capsid promoter was similar to that o bserved for a library of clones representing the entire viral genome. The genes provided by these 18 plasmids thus' represent the viral gene s necessary and sufficient to support expression from a late viral pro mpter in this transient expression assay.