Sequence, transcriptional mapping, and overexpression of p47, a baculovirus gene regulating late gene expression

A 2.8-kb region of the Autographa californica nuclear polyhedrosis virus genome was sequenced and found to contain an open reading frame (p47) which was capable of rescuing a previously characterized temperature-sensitive mutant, ts317 (S. Partington, H. Yu, A. Lu, and E. B. Carstens, Virology 157:91-102, 1990). Transcriptional mapping demonstrated that an early 4.2-kb RNA encoded the p47 open reading frame and probably overlapped the 39K delayed-early gene. The p47 open reading frame was cloned behind the polyhedrin promoter in a baculovirus transfer plasmid, which was then used to prepare a recombinant baculovirus overexpressing the p47 polypeptide. The overexpressed polypeptide was used to prepare p47-specific monoclonal antibodies. These antibodies detected a polypeptide of 47 kDa in A. californica nuclear polyhedrosis virus-infected cells, demonstrating that p47 is expressed as an authentic viral product. The p47 gene product was localized to the nucleus of infected cells, supporting the hypothesis that it is involved in regulating viral transcription at late times postinfection.