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The genes encoding the P39 and CG30 proteins of Bombyx mori nuclear polyhedrosis virus
Abstract:
We have cloned and analysed the transcriptional properties of two closely linked genes, p39 and cg30, of Bombyx mori nuclear polyhedrosis virus (BmNPV). These genes encode a structural polypeptide and a putative 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 eukaryotic polyadenylation signals and mapping 87 bp downstream of the translation 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 promoter sequences of another gene located further upstream of the p39 gene. 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-specific transcripts. The second is located 4 bp downstream of the CG30 translation termination codon. Transient expression assays show that the p39 gene sequences immediately upstream of the CG30 ORF can direct expression 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.
Insights
This study analyzes two linked genes, p39 and cg30, in Bombyx mori nuclear polyhedrosis virus (BmNPV). Researchers identified distinct transcriptional patterns and promoter activities, revealing insights into viral gene regulation.
Area of Science:
- Molecular Biology
- Virology
- Genetics
Background:
- Bombyx mori nuclear polyhedrosis virus (BmNPV) possesses complex gene expression strategies.
- Understanding viral gene regulation is crucial for developing effective antiviral therapies and biotechnological applications.
Purpose of the Study:
- To clone and analyze the transcriptional properties of two closely linked BmNPV genes, p39 and cg30.
- To characterize the regulatory elements and transcription initiation sites of these viral genes.
Main Methods:
- Gene cloning and analysis of transcriptional properties.
- RNA isolation, Northern blotting, and transient expression assays.
- Identification of polyadenylation signals and promoter sequences.
Main Results:
- The cg30 gene is transcribed early and late in infection, with its mRNA polyadenylated downstream of the stop codon.
- The p39 gene is transcribed as a 2.2 kb mRNA from upstream initiation sites, and a 6.5 kb RNA is also detected.
- Sequences upstream of the cg30 ORF function as a delayed-early promoter in the presence of the IE1 trans-activator.
Conclusions:
- The p39 and cg30 genes exhibit distinct transcriptional patterns and regulatory mechanisms within the BmNPV lifecycle.
- The identified promoter sequences provide insights into the temporal regulation of viral gene expression.
- This research contributes to the understanding of baculovirus gene organization and transcription.