Potent inhibition of Warner and Bloom helicases by DNA miner groove binding drugs

Maintenance of genomic integrity is vital to ail organisms, A number of hum an genetic disorders, including Werner Syndrome, Bloom Syndrome and Rothmun d-Thomson Syndrome, exhibit genomic instability with some phenotypic charac teristics of premature aging and cancer predisposition. Presumably the aber rant cellular and clinical phenotypes in these disorders arise from defects in important DNA metabolic pathways such as replication, recombination or repair. These syndromes are ail characterized by defects in a member of the RecQ family of DNA helicases. To obtain a better understanding of how thes e enzymes function in DNA metabolic pathways that directly influence chromo somal integrity, we have examined the effects of non-covalent DNA modificat ions on the catalytic activities of purified Werner (WRN) and Bloom (BLM) D NA helicases, A panel of DNA-binding ligands displaying unique properties f or interacting with double helical DNA was tested for their effects on the unwinding activity of WRN and BLM helicases on a partial duplex DNA substra te. The levels of inhibition by a number of these compounds were distinct f rom previously reported values for viral, prokaryotic and eukaryotic helica ses. The results demonstrate that BLM and WRN proteins exhibit similar sens itivity profiles to these DNA-binding ligands and are most potently inhibit ed by the structurally related minor groove binders distamycin A and netrop sin (K-i less than or equal to 1 mu M). The distinct inhibition of WRN and BLM helicases by the minor groove binders suggest that these helicases unwi nd double-stranded DNA by a related mechanism.