March 14, 2005
Although its name reads like a listing in a parts catalogue, EBNA3C is an essential protein produced by the common human pathogen, Epstein-Barr virus. The protein is one of four Epstein-Barr antigens that plays an essential role in the virus's reported ability to trigger our immune system's B cells to proliferate abnormally, which can contribute to the onset of Burkitt's lymphoma, Hodgkin's lymphoma, and other human cancers of our lymphatic system. Previous research shows EBNA3C specifically targets the retinoblastoma pathway, a chain of protein interactions that is best known for helping to regulate the cell cycle. Recently, NIDCR grantees and colleagues found that EBNA3C disrupts the inhibitory function of the p27 cell cycle regulator protein, stimulating the retinoblastoma pathway and promoting B cell proliferation. Now, as a followup to this finding, the researchers report in the March issue of Molecular and Cellular Biology that EBNA3C also directly targets the so-called SCFskp2 complex of proteins that is often deregulated in tumor cells, resulting in premature degradation of p27 through another process called the ubiquitin-proteasome pathway. This finding marks the first report of a viral protein influencing this specific complex of proteins, establishing a possible molecular mechanism to explain how the Epstein-Barr virus might influence the cell cycle of cancerous B cells.
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