"Epstein-Barr virus (EBV) is one of the most common human viruses in the world and is strongly linked to certain b-cell cancers like Burkitt's lymphoma as well as the epithelial cell cancer, nasopharyngeal carcinoma. EBNA1 is a protein coded in the Epstein-Barr virus and suspected to play a role in the development of cancer," says Lori Frappier, professor in medical genetics and microbiology at U of T and senior author of a paper in the April 1 issue of Molecular Cell.

"This research shows how EBNA1 interferes with natural cell growth regulation by binding to a particular protein in cells, causing them to continue growing and therefore increasing the risk of becoming cancerous."

Frappier explains that all cells contain the two proteins p53 and USP7 that work together to regulate cell growth. P53 is an important protein whose level in the cell determines whether cells will continue to proliferate or stop dividing and die. USP7 is a protein that binds to p53 and makes it stable. Under those conditions, cells stop growing and die, which is a natural state of cell regulation. Once EBNA1 is introduced to cells, however, this protein interferes with natural cell regulation by binding to USP7 and preventing its interaction with the p53 protein.

"Normally, p53 levels will increase in response to certain problems in the cell such as damaged DNA and this stops the cell from proliferating. Through binding USP7, EBNA1 keeps the p53 levels low so cells will continue to divide when they shouldn't, which means they're now more likely to develop into cancer," Frappier says.

"All viruses known to be able to cause cancer, like the human papillomavirus that causes cervical cancer for example, have
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31-Mar-2005