CELL-CYCLE VARIATION IN DNA MIGRATION IN PULSED-FIELD GEL-ELECTROPHORESIS

Pulsed-field electrophoresis is being used extensively in the gene map ping studies and in the analysis of DNA strand breakage by ionizing ra diation. We have evaluated the relationship between the fraction of S phase DNA in a cell population and its ability to modify the migration of DNA in pulsed-held gel electrophoresis. We have shown that increas ing the proportion of S phase DNA reduced the effective rate of migrat ion of MGH-U1 cellular DNA. This effect was observed after treatment w ith ionizing radiation or the restriction enzyme Not I. However, when radiation-induced damage was studied using intact cells, only the DNA with 70% S phase showed apparent differences in damage induction. Thes e studies therefore provide data to indicate the percentage of S phase cells at which overall DNA migration might be affected significantly.