Mechanism of induction of RNA tumor viruses by halogenated pyrimidines

Treatment of many types of mouse cells with halogenated pyrimidines causes them to begin to produce type C particles. The ability of these compounds to induce viruses from otherwise apparently uninfected cells implies that the genetic information for synthesis of these viruses is harbored within the cell in an unexpressed form. In what way the synthesis of virus is blocked in nonproducing cells is not known. Studies of the mechanism by which halogenated pyrimidines induce virus have inducated that the compounds must be incorporated into DNA: drugs which block DNA synthesis are able to decrease induction, whereas cells exposed to suboptimal concentrations of halogenated pyrimidines can be superinduced with white light. It was observed that the murine cell line, JLS V 9, is readily induced by halogenated pyrimidines to begin producing virus. New virus can be detected within 12 hours after addition of iododeoxyuridine (IdU) or bromodeoxyuridine (BrdU), and a treatment as short as 1 hour with the compounds is able to induce the cells to produce virus. The properties of this cell line were utilized to better understand the process of BrdU induction.