BINDING OF THE ESCHERICHIA-COLI UVRAB PROTEINS TO THE DNA MONOADDUCTSAND DIADDUCTS OF HYLAMINO-2,2,1-BICYCLOHEPTANE]DICHLOROPLATINUM(II) AND CISPLATIN - ANALYSIS OF THE FACTORS CONTROLLING RECOGNITION AND PROOF OF MONOADDUCT-MEDIATED UVRB-DNA CROSS-LINKING

The interactions of the Escherichia coli endonuclease UvrAB proteins w ith the DNA mono- and diadducts of both the cis-racemic thylamino-2,2, 1-bicycloheptane]dichloroplatinum(II (complex (1) under bar) and cispl atin (cis-diamminedichloroplatinum(II) (cis-DDP)), have been studied, Complex (1) under bar reacts faster with DNA than cis-DDP and gives mo noadducts with a longer lifetime (8 h 20 min chelation t(1/2) compared with 2 h 40 min for cis-DDP), Using pSP65 plasmid [H-3]DNA, the filte r binding assay was associated with the analysis of the nucleoprotein complexes to characterize the UvrAB recognition of the platinum adduct s and to demonstrate the occurrence of platinum-mediated DNA-protein c ross-linking, First, it is shown that the UvrAB proteins recognize the complex (1) under bar mono- and diadducts with a higher affinity than those of cis-DDP. Fifteen times more cis-DDP adducts per plasmid are required than complex (1) under bar adducts, to lead to similar UvrAB binding, However, the UvrAB proteins recognize monoadducts and diadduc ts of each complex with a similar affinity, Second, it is shown that U vrB is the protein involved in the nucleoprotein complexes formed from mono- and diadducts of complex (1) under bar and cis-DDP, This protei n is also partly cross-linked to DNA with a similar efficiency by mono adducts derived from complex (1) under bar and cis-DDP, However, as Uv rB has a greater affinity for the DNA adducts of complex (1) under bar than for those of cis-DDP, more UvrB-platinum-DNA cross-links are for med with complex 1 than with cis-DDP, This study, using a bacterial re pair system as a model, points to a possible strategy for making new c ytotoxic platinum complexes for mammalian cells.