title: Epstein-Barr virus nuclear antigen 3C regulates cyclin A/p27 complexes and enhances cyclin A-dependent kinase activity.
abstract: Epstein-Barr virus (EBV) nuclear antigen 3C (EBNA3C) is essential for primary B-cell transformation. In this report we show that cyclin A, an activator of S phase progression, bound tightly to EBNA3C. EBNA3C interacted with cyclin A in vitro and associated with cyclin A complexes in EBV-transformed lymphoblastoid cell lines. Importantly, EBNA3C stimulated cyclin A-dependent kinase activity and rescued p27-mediated inhibition of cyclin A/Cdk2 kinase activity by decreasing the molecular association between cyclin A and p27 in cells. Additionally, phosphorylation of the retinoblastoma protein, a major regulator of cell cycle progression, was enhanced both in vitro and in vivo in the presence of EBNA3C. Cyclin A interacted with a region of the carboxy terminus of EBNA3C, shown to be important both for stimulation of cyclin A-dependent kinase activity and for cell cycle progression. This provides the first evidence of an essential EBV latent antigen's directly targeting a cell cycle regulatory protein and suggests a novel mechanism by which EBV deregulates the mammalian cell cycle, which is of critical importance in B-cell transformation.
authors.affiliation: Department of Microbiology and Abramson Comprehensive Cancer Center, University of Pennsylvania Medical School, Philadelphia, Pennsylvania 19104, USA.
authors.forename: Jason S
authors.initials: JS
authors.lastname: Knight
authors.forename: Erle S
authors.initials: ES
authors.lastname: Robertson
mesh_terms: D000956:Antigens, Viral / Q000378:metabolism*; D001402:B-Lymphocytes / Q000821:virology; D018797:Cell Cycle Proteins / Q000378:metabolism*; D002461:Cell Line, Transformed; D002467:Cell Nucleus / Q000378:metabolism; D002472:Cell Transformation, Viral; D019925:Cyclin A / Q000378:metabolism*; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases / Q000378:metabolism*; D019309:Epstein-Barr Virus Nuclear Antigens; D005786:Gene Expression Regulation; D006367:HeLa Cells; D006801:Humans; D025521:Tumor Suppressor Proteins / Q000378:metabolism*; D020798:Two-Hybrid System Techniques
chemical_list: D000956:Antigens, Viral; D018797:Cell Cycle Proteins; D019925:Cyclin A; C498774:EBNA-3C, epstein-barr virus; D019309:Epstein-Barr Virus Nuclear Antigens; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases