title: Adenovirus E4orf4 protein downregulates MYC expression through interaction with the PP2A-B55 subunit.
abstract: The adenovirus E4 open reading frame 4 (E4orf4) protein is a multifunctional viral regulator that is involved in the temporal regulation of viral gene expression by modulating cellular and viral genes at the transcription and translation levels and by controlling alternative splicing of adenoviral late mRNAs. When expressed individually, E4orf4 induces apoptosis in transformed cells. Using oligonucleotide microarray analysis, validated by quantitative real time PCR, we found that MYC (also known as c-Myc) is downregulated early after the induction of E4orf4 expression. As a result, Myc protein levels are reduced in E4orf4-expressing cells. MYC downregulation is observed both when E4orf4 is expressed individually and within the context of viral infection. E4orf4 reduces MYC transcription but does not affect transcriptional elongation or RNA stability. An interaction with the PP2A-B55 subunit is required for the downregulation of MYC by E4orf4. Since Myc overexpression was previously shown to inhibit adenovirus replication, the downregulation of Myc by E4orf4 would contribute to efficient virus infection.
authors.affiliation: The Gonda Center of Molecular Microbiology, Faculty of Medicine, Technion-Israel Institute of Technology, Bat Galim, Haifa 31096, Israel. tamark@tx.technion.ac.il
authors.forename: Haggit
authors.initials: H
authors.lastname: Ben-Israel
authors.forename: Rakefet
authors.initials: R
authors.lastname: Sharf
authors.forename: Gideon
authors.initials: G
authors.lastname: Rechavi
authors.forename: Tamar
authors.initials: T
authors.lastname: Kleinberger
mesh_terms: D000256:Adenoviridae / Q000235:genetics / Q000378:metabolism*; D002453:Cell Cycle; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D015536:Down-Regulation; D005091:Exons; D015967:Gene Expression Regulation, Viral; D006801:Humans; D008954:Models, Biological; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis; D016366:Open Reading Frames; D054648:Protein Phosphatase 2 / Q000737:chemistry*; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism*; D014764:Viral Proteins / Q000235:genetics* / Q000502:physiology*
chemical_list: C121517:E4orf4 protein, adenovirus; C512974:PPP2R2A protein, human; D016271:Proto-Oncogene Proteins c-myc; D014764:Viral Proteins; D054648:Protein Phosphatase 2