BINDING OF IXR1, A YEAST HMG-DOMAIN PROTEIN, TO CISPLATIN-DNA ADDUCTS IN VITRO AND IN VIVO

摘要: Ixr1 is a yeast HMG-domain protein that binds specifically to DNA adducts formed by the antitumor drug cisplatin. Interruption of IXR1 gene in desensitizes cells This effect unrelated natural function Ixr1, which repress transcription COX5b. interacts and preferentially with modified In present work, was purified from clone expressed Escherichia coli. The dissociation constant for binding site-specifically 92-bp probe containing single cis-[Pt(NH3)2{d(GpG)-N7(1) -N7(2)}] intrastrand cross-link measured be 2.5 (+/- 0.1) x 10(-7) M, similar found HMG1. at least an order magnitude more tightly cisplatin-DNA than unmodified DNA. Hydroxyl radical footprinting revealed protects area platinated approximately 15 bp size centered platinum adduct. proteins has been proposed divert these their DNA-binding sites, disrupting transcription. hypothesis tested yeast. not titrated away Cox5b promoter sufficiently well disrupt either mRNA genomic or beta-galactosidase under control plasmid transformed into