Regulated expression of the feline panleukopenia virus P38 promoter on extrachromosomal FPV/EBV chimeric plasmids

Feline panleukopenia virus/Epstein-Barr virus (FPV/EBV) chimeric expression plasmids were constructed to study regulation of the structural protein gene of the parvovirus, FPV, in a homologous cell culture system. Detection and quantitation of activity from the native FPV promoter, P38, was facilitated by fusing the Escherichia coli lacZ gene with the FPV structural protein gene. Feline cell lines which stably maintained these plasmids extrachromosomally were established. Constitutive β-galactosidase activity was low but increased up to 40-fold after infection with FPV. Expression of β-galactosidase was only detected when the FPV/lacZ gene was oriented in the same transcriptional direction as the Epstein-Barr virus gene coding for EBNA-1. When a small open reading frame upstream of the FPV/lacZ initiation codon was detected, β-galactosidase expression increased another 4.7- to 26-fold. These changes in β-galactosidase activity indicate that expression of the FPV structural protein gene is regulated both transcriptionally and posttranscriptionally.