Repair Synthesis of DNA in HeLa and L-celis Following Treatment with Methylnitrosourea or Ultraviolet Light

Abstract

Repair synthesis of DNA was measured in HeLa and L-cells following treatment with either ultraviolet (U.V.) light or methylnitrosourea (MNUA). HeLa cells exhibited 10 and 30 times more repair synthesis after U.V. light and MNUA treatment, respectively. HeLa cells were considerably more sensitive than L-cells to U.V. light and MNUA. MNUA formed the same kinds and amount of methylation products in the DNA of both cell lines. During post-treatment incubation, the overall rate of loss of these products from the DNA was similar in both cell lines. The minor product 3-methyladenine was preferentially removed from the DNA of HeLa cells but not L-cells. When previous studies with Chinese hamster and normal human fibroblasts were considered along with the present results it appeared that rodent cells not only exhibited less repair synthesis than human cells, but they were less sensitive to methylating agents and ultraviolet light.