Characterization of the baculovirus Bombyx mori nucleopolyhedrovirus gene homologous to the mammalian FGF gene family

We characterized a gene of the baculovirus Bombyx mori nucleopolyhedrovirus ( BmNPV) homologous to the mammalian. broblast growth factor (FGF) family. We termed it vfgf, and examined its transcription and the properties of the gene product (vFGF). RT-PCR analysis showed that vfgf is one of the baculovirus early genes, although there are no consensus sequences of the baculovirus early gene promoters. 50-RACE analysis revealed that its transcription started at 10 nucleotides upstream of the translation start codon. vFGF has a hydrophobic amino terminus (similar to16 amino acids), which is a typical signal sequence. As expected, vFGF was efficiently secreted from BmNPV-infected BmN cells. Because possible glycosylation sites are found at positions 44 (Asn) and 171 ( Asn), we examined whether BmNPV vFGF is glycosylated or not. Cleavage of recombinant vFGF with PNGase F revealed that BmNPV vFGF was glycosylated. We also found that secretion of vFGF is completely blocked by the treatment of Tunicamycin, which blocks N-linked glycosylation. This is the first report to characterize a virus-encoded FGF.