The rate of elution of DNA during non-denaturing filter elution (NFE) often correlates with cell sensitivity to radiation.
The elution rate is influenced by two cellular factors: chromatin structure and the number of DNA double-strand breaks (DSBs) produced in an intact cell by ionizing radiation.
To determine which of the above factors is relevant to cell radiosensitivity, four assays were used to measure induction of DNA damage in three cell lines varying in radiosensitivity (V79, CHO, and L5178Y-R).
Each of the assays, neutral filter elution (NFE), DNA precipitation, constant (CFGE) and pulsed field gel electrophoresis (PFGE) have different physical basis for DNA damage measurement and might be differently affected by chromatin structure.
Three of the methods used to measure DNA double-strand breaks gave different results: NFE was dependent on cell type and location of DNA relative to the replication fork, and the precipitation assay was independent of both cell type and replication status.
Pulsed field gel electrophoresis produced the same results as constant field gel electrophoresis for the 3 cell lines examined.
Only NFE showed differences in sensitivity which correlated with cell survival following irradiation.
The results suggest that there is the same initial amount of DSBs in cells from all three lines and that the sensitivity to radiation is determined by some additional factors, probably chromatin structure.