Certain donor plasmid vectors such as pFastBac™1 and pFastBac™ Dual lack a cis DNA element upstream of the polh translation start codon (ATG) present in wild type (wt) Autographa californica multiple nucleopolyhedrovirus (AcMNPV), and contain a SV40 pA fragment. When a cis DNA element is inserted upstream of the 50 bp polh promoter and SV40 pA was replaced with a AcMNPV polh pA signal in pFastBac™1 and pFastBac™Dual, certain protein expression levels in High Five™ cells using the Bac-to-Bac® system reached that of the wt AcMNPV.