Fig. 5

Subtyping of FA primary fibroblasts by functional complementation with FA retroviruses. The indicated cell lines were infected with either no retrovirus, pMMP-FAA, pMMP-FAC, or pMMP-nlsLacZ, as indicated. Infected cells were treated with MMC (25 ng/ml) for 48 hr. Cells were stained with propidium iodide and analyzed by FACS, as described in Materials and Methods. The percentage of cells in the G2/M phase of the cell cycle was determined by analyzing data with the computer program modFITLT. The mean values shown were calculated from three separate retroviral infection experiments. Because primary FA fibroblasts did not undergo apoptosis in response to MMC, we chose to study these lines by assessing G2 accumulation. In contrast, EBV-transformed lymphoblast lines undergo rapid cell death in response to MMC, and correction of these cells can be scored by an XTT cell survival assay (Table 1).