Transcription Factor YY1 Is a Vaccinia Virus Late Promoter Activator

• Published in: The Journal of biological chemistry 1999-12, Vol.274 (50), p.35662-35667
• Main Authors: Broyles, S S, Liu, X, Zhu, M, Kremer, M
• Format: Article
• Language: English
• Subjects: Base Sequence; Cell Line; DNA-Binding Proteins - metabolism; Erythroid-Specific DNA-Binding Factors; Escherichia coli; Gene Expression Regulation, Viral; HeLa Cells; Humans; Molecular Sequence Data; Mutagenesis, Site-Directed; Nuclear Proteins - metabolism; Poxvirus; Promoter Regions, Genetic; Recombinant Proteins - metabolism; Transcription Factors - metabolism; Vaccinia virus; Vaccinia virus - genetics; YY1 protein; YY1 Transcription Factor
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.274.50.35662

Vaccinia virus has a DNA genome, yet replicates in the cytoplasmic compartment of the cell. We previously described the identification of a cellular protein having high affinity for vaccinia virus late promoter DNA. Sequence substitutions in the vaccinia I1L promoter were used to define a 5-nucleotide block at the transcription initiation site as essential for interaction with the protein. Within this sequence is the recognition motif for the nuclear transcription factor YY1. This factor regulates a multitude of cellular promoters, as an activator of transcription, as a repressor, or as an initiator element-binding protein. Antibodies directed against YY1 were used to show that YY1 copurified with the vaccinia late promoter-binding protein and was present in late promoter-protein complexes in gel supershift assays. Bacterially expressed YY1 also bound specifically to late promoter DNA. A dinucleotide replacement within the YY1 recognition motif directly adjacent to the transcription start site severely reduced the affinity of YY1 for the I1L promoter in vitro and impaired I1L promoter-dependent transcription in vivo . The intracellular localization of YY1 was shown by immunofluorescence microscopy to shift from primarily nuclear to the cytoplasm after vaccinia infection. These results indicate that YY1 has a positive role in the regulation of vaccinia virus late gene transcription and suggest that poxviruses have adapted cellular initiator elements as a means of regulating viral gene expression. This is the first identifiable cellular protein implicated in poxvirus transcription.