The Implication of Repair Processes in the Mechanism of DNA Integration by Lymphoma Cells

Abstract
The uptake and integration of exogenous 3H-IUdR labelled DNA by irradiated cultures of an IUdR resistant mutant of P338F cells has been studied by preparative CsCl density gradient centrifugation. 10−2 M hydroxyurea was found to inhibit DNA synthesis as measured by uptake of 14C cytidine, but did not inhibit the integration of the exogenous DNA. This implies that enzymes involved in integration and repair are different from those concerned with DNA synthesis. ‘Repair’ synthesis of DNA has been demonstrated after 150 and 400 rads of x-rays. The amount of DNA uptake and integration was higher in irradiated cells and increased with increasing dose. Density-gradient centrifugation of DNA integrated into irradiated cells suggests the possibility of the release of nucleases from irradiated cells. The survival of the irradiated cells was unaffected by the integration of exogenous DNA.