Purification of the HMG1 protein and investigation of its interactions with diepoxide cross-linked DNA

HMG 1 is a nonhistone chromosomal protein that binds preferentially to some types of globally modified DNA. HMG I has been implicated in the cellular response to the anti~cer agent cisplatin, functioning to block excision repair of specific distorted platinated DNA lesions and resulting in enhanced cytotox..icity. We have investigated whether other DNA-binding agents also produce lesions that are recognized by HMG I. Specifically, we used polyacrylamide gel shift assays to monitor the potential HMG I binding of diepoxybutane interstrand cross-links, which have been suggested to induce DNA bending. We isolated the native protein from chicken erythrocytes and expressed engineered HMG domain proteins in E. coli. Preliminary studies support weak. binding of the HMG A domain protein to the cross-linked DNA oligomer.