Identification of additional genes that influence baculovirus late gene expression

We were unable to confirm transient late gene expression using constructs of 18 genes that had been reported to support Autographa californica multinucleocapsid nucleopolyhedrovirus (AcMNPV) late gene expression when transfected into Spodoptera frugiperda cells [Lu, A., and Miller, L. K. (1995). J. Virol. 69, 975-982]. Three genes (orf66, orf68, and orf41) were included, all or in part, in the constructs used in that study, but they had not been independently tested. Therefore we investigated these and neighboring orfs for their influence on late gene expression. We found that orf41 was required for late gene expression and that sequences within orf45 appeared to be required for the expression of orf41. Although orf66 and orf68 did not appear to affect late gene expression, orf69 stimulated expression. orf69 was found to have high homology to recent entries in GenBank from a variety of organisms. In addition, it was found that orf121, which was shown to be involved in early gene expression, and the viral homolog of pcna did not influence late gene expression.