THE GENES ENCODING THE P39 AND CG30 PROTEINS OF BOMBYX-MORI NUCLEAR POLYHEDROSIS-VIRUS

We have cloned and analysed the transcriptional properties of two clos ely linked genes, p39 and cg30, of Bombyx mori nuclear polyhedrosis vi rus (BmNPV). These genes encode a structural polypeptide and a putativ e transcriptional regulator of the virus, respectively, The cg30 gene is transcribed prior to and after DNA replication from a site located within the ORF of the adjacent p39 gene. Its transcription product, a 1.3 kb mRNA, is polyadenylated at a site containing consensus eukaryot ic polyadenylation signals and mapping 87 bp downstream of the transla tion termination codon for CG30. During the later stages of infection, two additional RNAs, 2.2 and 6.5 kb, are also transcribed through the cg30 gene, The 2.2 kb RNA, representing the mRNA that encodes P39, is initiated from three relatively closely spaced sites located upstream of the P39 ORF. The 6.5 kb RNA is apparently transcribed from the pro moter sequences of another gene located further upstream of the p39 ge ne. The 2.2 and 6.5 kb transcripts have two polyadenylation sites. The first site is the same as the one used to generate the cg30 gene-spec ific transcripts. The second is located 4 bp downstream of the CG30 tr anslation termination codon, Transient expression assays show that the p39 gene sequences immediately upstream of the CG30 ORF can direct ex pression of a reporter gene when the latter is co-transfected with the gene encoding the early baculovirus trans-activator IE1. Thus, these sequences behave as a delayed-early baculovirus gene promoter.