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Endogenous retroviruses are the remnant DNA of a past viral infection. Retroviruses (like the AIDS virus or HTLV1, which causes a form of leukemia) make a copy of their own viral DNA and insert it into their host's DNA. This is how they take over the cellular machinery of a cell and use it to manufacture new copies of the virus. Sometimes, the cell that get’s infected by such a virus is an immature egg cell in the ovary of a female animal. Such cells can be stored in a state of suspended animation or dormancy for as much as...

Close window Published online: 31 October 2006; | doi:10.1038/news061030-4 Ancient human virus resurrectedVirus from distant past may throw light on role of retroviruses in cancer.Helen Pearson Retroviruses, of which HIV is a modern example, infiltrated our genome long ago. RUSSELL KIGHTLEY / SCIENCE PHOTO LIBRARY Researchers in France have recreated a 5-million-year-old virus whose remains are now found littered across the human genome. The ancient virus could help us to understand how these genetic remnants contribute to cancer. The virus is of a type called a retrovirus, which can insert copies of its genetic material into our own DNA....