title: Potent inhibition of DNA unwinding and ATPase activities of pea DNA helicase 45 by DNA-binding agents.
abstract: Pea DNA helicase 45 (PDH45) is an ATP-dependent DNA unwinding enzyme, with intrinsic DNA-dependent ATPase activity [Plant J. 24 (2000) 219]. We have determined the effect of various DNA-binding agents, such as daunorubicin, ethidium bromide, ellipticine, cisplatin, nogalamycin, actinomycin C1, and camptothecin on the DNA unwinding and ATPase activities of the plant nuclear DNA helicase PDH45. The results show that all the agents except actinomycin C1, and camptothecin inhibited the helicase (apparent K(i) values ranging from 1.5 to 7.0 microM) and ATPase (apparent K(i) values ranging from 2.5 to 11.9 microM) activities. This is the first study to show the effect of various DNA-binding agents on the plant nuclear helicase and also first to demonstrate inhibition of any helicase by cisplatin. Another striking finding that the actinomycin C1 and ellipticine act differentially on PDH45 as compared to pea chloroplast helicase suggests that the mechanism of DNA unwinding could be different in nucleus and chloroplast. These results suggest that the intercalation of the inhibitors into duplex DNA generates a complex that impedes translocation of PDH45, resulting in both the inhibitions of unwinding activity and ATP hydrolysis. This study would be useful to obtain a better understanding of the mechanism of plant nuclear DNA helicase unwinding and the mechanism by which these agents can disturb genome integrity.
authors.affiliation: Plant Molecular Biology Group, International Centre for Genetic Engineering and Biotechnology, P.O. Box 10504, Aruna Asaf Ali Marg, New Delhi 110 067, India.
authors.forename: Xuan Hoi
authors.initials: XH
authors.lastname: Pham
authors.forename: Narendra
authors.initials: N
authors.lastname: Tuteja
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000187:drug effects*; D000255:Adenosine Triphosphate / Q000737:chemistry; D000818:Animals; D002467:Cell Nucleus / Q000201:enzymology; D002736:Chloroplasts / Q000201:enzymology; D002945:Cisplatin / Q000737:chemistry / Q000494:pharmacology; D004247:DNA / Q000737:chemistry* / Q000378:metabolism; D004265:DNA Helicases / Q000737:chemistry* / Q000187:drug effects; D003630:Daunorubicin / Q000737:chemistry / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004611:Ellipticines / Q000737:chemistry / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000737:chemistry* / Q000494:pharmacology; D004996:Ethidium / Q000737:chemistry / Q000494:pharmacology; D007364:Intercalating Agents / Q000737:chemistry* / Q000494:pharmacology; D009621:Nogalamycin / Q000737:chemistry / Q000494:pharmacology; D019384:Nucleic Acid Synthesis Inhibitors / Q000737:chemistry / Q000494:pharmacology; D018532:Pisum sativum; D010940:Plant Proteins / Q000737:chemistry* / Q000187:drug effects; D051381:Rats
chemical_list: D004611:Ellipticines; D004791:Enzyme Inhibitors; D007364:Intercalating Agents; D019384:Nucleic Acid Synthesis Inhibitors; D010940:Plant Proteins; C034192:ellipticine; D000255:Adenosine Triphosphate; D004247:DNA; D000251:Adenosine Triphosphatases; D004265:DNA Helicases; D004996:Ethidium; D009621:Nogalamycin; D002945:Cisplatin; D003630:Daunorubicin