The detection of DNA-protein complexes in vitro by an immunological assay

We have developed an immunological assay to detect DNA-protein complexes (DPCs) in cell cultures treated with environmental toxicants. The assay uses an antiserum developed against K(2)CrO(4)-induced DPCs, which recognizes an acidic protein with a molecular weight of 95 kDaltons. The method uses a filter-binding assay to trap the DPCs from SDS-lysed cell cultures on polycarbonate filters, after which they are immunologically probed with the DPC antiserum. Cultures of Chinese hamster ovary cells were treated with K(2)CrO(4), formaldehyde or UV irradiation. DPCs were detected immunologically in cells treated with K(2)CrO(4) or UV irradiation, but not in those treated with formaldehyde. These results were similar to those obtained when DPCs were detected by filter-binding assay using radiolabelled cell cultures to measure the adherence of protein and DNA to the filters. In addition, both methods gave analogous dose responses of DPC formation in K(2)CrO(4)-treated cells. This novel immunological assay for detecting DNA lesions allows the rapid analysis of samples, which do not need to be radiolabelled, and thus it may have an application as a non-invasive test to screen for DNA-protein complexes.