Identification of a viral gene encoding a ubiquitin-like protein.
The baculovirus Autographa californica nuclear polyhedrosis virus (AcMNPV, which is representative of the MNPV subtype in which the virions may contain many nucleocapsids within a single viral envelope) encodes a protein, v-ubi, that has 76% identity with the eukaryotic protein ubiquitin. Transcriptional mapping indicated that the gene for v-ubi was transcribed during the late phase of viral infection. Two transcriptional start sites potentially encoding v-ubi were identified. Both sites were contained within a sequence motif common to baculovirus late genes. A recombinant virus, AcUbi-beta Gal, encoding a ubiquitin-beta-galactosidase fusion protein was constructed to monitor the temporal regulation of v-ubi gene during viral infection. The fusion protein was expressed maximally at 14-18 hr postinfection, consistent with its classification as a late protein. The amount of ubiquitin-beta-galactosidase fusion protein that accumulated in AcUbi-beta Gal-infected cells by 48 hr postinfection was approximately 14% of the level of beta-galactosidase that was synthesized under control of the polyhedrin promoter. Transcriptional analysis confirmed that synthesis of the fusion protein was directed by the v-ubi gene promoter. AcUbi-beta Gal also produced normal levels of authentic viral ubiquitin message. Southern blot analysis of AcUbi-beta Gal and 15 additional isolates revealed that the fusion sequences had not recombined at the ubiquitin locus. A polyubiquitin gene was isolated and sequenced from Spodoptera frugiperda, a lepidopteran host cell line for AcMNPV. The predicted amino acid sequence of the product of the host gene is identical to animal ubiquitin.
Guarino
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Department of Entomology, Texas Agricultural Experiment Station, College Station 77843.
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D004279:DNA, Viral / Q000235:genetics; D005814:Genes, Viral; D006801:Humans; D007304:Insect Viruses / Q000235:genetics*; D008969:Molecular Sequence Data; D009036:Moths; D015183:Restriction Mapping; D012689:Sequence Homology, Nucleic Acid; D014452:Ubiquitins / Q000235:genetics*; D014764:Viral Proteins / Q000235:genetics*; D015678:Viral Structural Proteins / Q000235:genetics*; D014771:Virion / Q000235:genetics
D004279:DNA, Viral; D014452:Ubiquitins; D014764:Viral Proteins; D015678:Viral Structural Proteins