Molecular analysis of an occlusion body protein from Culex nigripalpus nucleopolyhedrovirus (CuniNPV)

CUN085 is an occlusion body (OB) protein from the nucleopolyhedrovirus of Culex nigripalpus (CuniNPV). SDS–PAGE analysis indicated that the CuniNPV OB protein is about 3 times the size (∼90 kDa) of characterized nucleopolyhedrovirus (NPVs) and granulovirus OB proteins. Rapid amplification of cDNA ends (RACE), RNase protection assay, real-time PCR, and protein sequencing were used to characterize CUN085 from CuniNPV. RACE data revealed that the transcriptional start and termination sites for the CUN085 gene yielded a polypeptide comprised of 822 amino acids indicating that translation initiates within a larger 882 amino acid open reading frame that was originally predicted from the CuniNPV genome sequence. Transcription of CUN085 started at a consensus baculovirus late transcription start site TAAG at nucleotide position 75433 of the CuniNPV genome sequence. RNase protection assays and quantitative real-time PCR show that the CUN085 transcript is first detected in mosquito larvae at approximately 6 h after infection with CuniNPV and its prevalence increased progressively over the subsequent 18 h.