Abstract
The second and third lectures were devoted to viral oncogenesis. Since the beginning of the 20th century, several experimental models have formally demonstrated that certain animal tumors are transmissible by ultra-filtering agents, which we now know to be viruses. The best-studied example is Rous sarcoma. The ability of retroviruses to capture genes from the infected host cell led to the discovery of the first dominant oncogenes. But retroviruses, with their ability to integrate close to cellular genes, can also lead to the overexpression of key growth regulators, such as the Myc gene. This is known as insertional mutagenesis. The capture of oncogenes, or the insertion of proviruses in their vicinity, are exceptional mechanisms in humans. There is, however, one oncogenic retrovirus, HTLV-I, whose biology has been presented in detail, in particular the role of its transcriptional activator Tax in the proliferation of infected or leukemic cells.
