Alpha-radiation-induced amplification of integrated SV40 sequences is mediated by a trans-acting mechanism

Treatment of Chinese hamster embryo cells with alpha irradiation (4 MeV, emitted by 241americium) induces a 15-fold amplification of integrated SV40 sequences. The extent of amplification depends on the dose of irradiation and on the presence of a functional T-antigen encoded by the SV40 A gene. The inducing signal can be transmitted to a non-irradiated nucleus following cell fusion. Amplification is therefore the result of some trans-acting process, and this could explain how SV40 amplification can occur after doses of alpha irradiation that are too low to cause direct DNA damage within the SV40 replicon.