Search for Novel Anti-cancer Drugs Targetting DNA Replication and Repair

点击翻译按钮获取中文摘要

We have screened more than one hundred of culture supernatants of Actinomycetes and Eumycetes using cell-free systems for SV40 DNA replication and the nucleotide excision repair (NER) with UV-irradiated SV40 minichromosomes to obtain either inhibitors or stimulators for DNA replication and repair. As s result of these screening, we obtained a couple of samples for replication inhibitors and NER inhibitors.One of the replication inhibitors (RK606) was purified, and its structure was identified as a kind of soybean saponin (soyasaponin II). RK606 also inhibited SV40 DNA replication with purified proteins, therefore, we examined the effect of RK606 on individual enzymes and proteins. It turned out that RK606 specifically inhibited DNA helicase activity of SV40 T antigen. Interestingly, a cellular DNA helicase was not inhibited by this compound, indicating that RK606 might be a specific inhibitor of T antigen helicase. To our knowledge, this is the first inhibitor besides ATP analogues for any DNA helicase.One of the repair inhibitors (RK679) was examined for its stability at different pH and for its extractability by several solvents. The behaviors of the repair inhibitor were similar to those of some kinds of tyrosine kinase inhibitors, genistein and daizein, therefore, we checked the effect of these tyrosine kinase inhibitors on cell-free NER assay. However, we could not find any effect of these compounds on NER,suggesting that RK679 is not either genistein or daizein but is rather different compound.