Identification and characterization of vlf-1, a baculovirus gene involved in very late gene expression

• Published in: Journal of Virology 1994-12, Vol.68 (12), p.7746-7756
• Main Authors: McLachlin, J.R. (University of Georgia, Athens, GA.), Miller, L.K
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Animals; Autographa californica; Base Sequence; Cell Line; Cloning, Molecular; COMPOSICION QUIMICA; COMPOSITION CHIMIQUE; DNA Nucleotidyltransferases - genetics; EXPRESION GENICA; EXPRESSION DES GENES; GENE; Gene Expression Regulation, Viral; GENES; Genes, Regulator; Genes, Viral; Genetic Markers; GENETICA; GENETIQUE; Humans; Integrases; Kinetics; Molecular Sequence Data; Mutation; Nucleopolyhedrovirus - genetics; Nucleopolyhedrovirus - metabolism; Open Reading Frames; Plasmids; PROTEINAS; PROTEINE; Restriction Mapping; SECUENCIA NUCLEICA; Sequence Homology, Amino Acid; SEQUENCE NUCLEIQUE; Spodoptera; SPODOPTERA FRUGIPERDA; Temperature; Transcription Factors - biosynthesis; Transcription Factors - genetics; Transcription Factors - isolation & purification; Viral Proteins - biosynthesis; Viral Proteins - genetics; Viral Proteins - isolation & purification; Viral Structural Proteins; VIRUS; VIRUS POLIEDROSIS NUCLEAR; VIRUS POLYEDROSE NUCLEAIRE
• ISSN: 0022-538X; 1098-5514
• DOI: 10.1128/jvi.68.12.7746-7756.1994

We have identified a gene required for strong expression of the polyhedrin gene by characterizing a mutant, tsB837, of the baculovirus Autographa californica nuclear polyhedrosis virus (AcMNPV) which is temperature sensitive (ts) for occluded virus production at the nonpermissive temperature. Marker rescue experiments utilizing an overlapping set of AcMNPV genomic clones revealed that the gene responsible for the ts mutant phenotype mapped to a region between 46 and 48 map units. Fragments (2.2 kb) from both wild-type AcMNPV and tsB837 genomes spanning the mutated region were sequenced, and a single nucleotide difference was observed. This mutation is predicted to substitute a single amino acid within a 44.4-kDa polypeptide. Analysis of protein synthesis in wild-type- and mutant-infected cells at the nonpermissive temperature indicated that polyhedrin synthesis was dramatically reduced in the mutant. Northern (RNA) blot analysis revealed that the mutant had markedly reduced levels of polyhedrin transcripts. Transcripts of another very late gene, p10, were also reduced but to a lesser degree. The transcription of two late genes (603 ORF and vp39) was neither reduced nor temporally delayed. Thus, the gene encoding this very late expression factor, designated vlf-1, regulates the levels of very late gene transcripts, and the tsB837 mutation affects the levels of polyhedrin gene transcripts more strongly than those of p10 transcripts. The product of the newly identified gene has a surprising but significant relationship to a family of integrases and resolvases