Polyhedrin promoter

High levels of heterologous gene expression are often achieved by using the strong polyhedrin promoter of the Astographa californica nuclear polyhedrosis virus (AcNPV) ... 

When the virus was used to infect a known, fully permissive cell line from Spodoptera frugiperdaf both genes were expressed. CAT activity was detected early in the infection at about six hours, a not surprising result since the RSV LTR contains an RNA polymerase II promoter and this enzymatic activity, pre-existing in the cell, should be amongst the first to act on the viral chromosome. Late in the infection, at the time that the polyhedrin promoter is known to become active, P-galactosidase activity was detected. 

The authors were able to detect what they felt was a very low level of DNA replication in Drosophila. The important point is that the detection of CAT activity in Drosophila demonstrates that the virus is entering the cells and is being uncoated to free the genome for transcriptional activity. The presumptive reason for lack of (J-galactosidase activity is the absence of cellular or viral products necessary for polyhedrin promoter activity. 

Juvenile hormone esterase was also expressed under control of the polyhedrin promoter in BmNPV (Hanzlik, Kamita, Hammock and Maeda, unpublished). A 3kbp insert from the clone 3hvl, was introduced into BmNPV 42). The in vivo expression of AcNPV and BmNPV constructs were compared side by side on injection of B. mori, T. ni and H. virescens (Table II). 

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