Epstein-Barr virus EBNA3C can disrupt multiple cell cycle checkpoints and induce nuclear division divorced from cytokinesis.
Expression of EBNA3C is essential for the immortalization of B cells by EBV in vitro and, in co-operation with activated ras, EBNA3C has oncogenic activity in primary rodent fibroblasts. This suggested that this viral oncoprotein might disrupt the cyclin/CDK-pRb-E2F pathway, which regulates cell cycle progression at the restriction point (R-point) in G1 of the proliferation cycle. An assay was established in which transfected EBNA3C-positive cells could be sorted and simultaneously analysed for their distribution in the cell cycle. This revealed that in NIH3T3 fibroblasts compelled to arrest by serum-withdrawal, EBNA3C induces nuclear division that is often divorced from cytokinesis and so produces bi- and multinucleated cells. This was confirmed using the ecdysone-inducible system for expression of EBNA3C in human U2OS cells and by microinjection of expression vectors into NIH3T3 and U2OS. Further analysis revealed that in the inducible system, EBNA3C expression inhibits the accumulation of p27(K1P1) but not the dephosphorylation of pRb. Experiments using the microtubule destabilizing drug nocodazole, showed that EBNA3C could abrogate the mitotic spindle checkpoint.
Parker
G A
GA
Section of Virology and Cell Biology, Imperial College of Science, Technology and Medicine, London, UK.
Touitou
R
R
Allday
M J
MJ
D016475:3T3 Cells; D000818:Animals; D002453:Cell Cycle / Q000502:physiology; D018797:Cell Cycle Proteins; D002455:Cell Division / Q000502:physiology; D002460:Cell Line; D002461:Cell Line, Transformed; D002467:Cell Nucleus / Q000502:physiology*; D016895:Culture Media, Serum-Free; D050760:Cyclin-Dependent Kinase Inhibitor p27; D019309:Epstein-Barr Virus Nuclear Antigens / Q000096:biosynthesis / Q000502:physiology*; D015726:Giant Cells / Q000378:metabolism*; D006801:Humans; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D010766:Phosphorylation; D011003:Ploidies; D016160:Retinoblastoma Protein / Q000378:metabolism; D008941:Spindle Apparatus / Q000378:metabolism; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins
C493961:Cdkn1b protein, mouse; D018797:Cell Cycle Proteins; D016895:Culture Media, Serum-Free; D019309:Epstein-Barr Virus Nuclear Antigens; D008869:Microtubule-Associated Proteins; D016160:Retinoblastoma Protein; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27