Most people are infected for life with Epstein-Barr virus (EBV), a virus that is associated with a growing list of cancers due to its ability to efficiently immortalize cells. We are interested in the proteins and mechanisms involved in the replication and mitotic segregation of Epstein-Barr virus (EBV) genomes and in EBV-mediated cell immortalization. Several of our studies involve the EBNA1 protein of EBV, which is the only viral needed to replicate and maintain EBV genomes in human cells and which appears to directly contribute to cell transformation. Using proteomics approaches, we have discovered the interaction of EBNA1 with host proteins that control cell proliferation and apoptosis (USP7 and CK2) and with host nucleosome associated proteins that regulate DNA replication and transcription through histone modifications. In addition, we found that EBNA1 disrupts the host PML nuclear bodies required for apoptosis and DNA repair, thereby promoting cell survival with DNA damage. We are currently studying these interactions to better understand how they facilitate EBV infection and/or contribute to EBV-induced cancers, including lymphomas, nasopharyngeal carcinoma and gastric carcinoma. Our studies on the disruption of PML nuclear bodies are also being applied to libraries of proteins from Epstein-Barr virus, cytomegalovirus and herpes simplex virus in order to better understand the mechanisms by which DNA viruses target these nuclear structures. Finally, we are also using proteomic approaches to characterize MCM replicative helicase complexes in human cells and how these contribute to genomic DNA replication. This lead to the discovery of a previously unrecognized MCM protein (MCMBP), that forms part of an alternative MCM complex, and whose functions and biochemistry are now being studied.
Studies in the Frappier laboratory involve a variety of methodologies, including proteomics approaches (eg. TAP-tagging and protein identification by mass spectrometry), protein biochemistry, functional assays in human cells, RNA interference, immunoflurescence microscopy and structure determination by X-ray crystallography.