Novel molecular mechanism for actinomycin D activity as an oncogenic promoter G-quadruplex binder.
Actinomycin D (ActD) is a natural antibiotic that inhibits the transcription of genes by interacting with a GC-rich duplex, a single-stranded or hairpin form of DNA, and then interfering with the action of RNA polymerase. In this study, we identified a novel molecular mechanism of anticancer activity of ActD as an oncogenic c-Myc promoter G-quadruplex binder. ActD selectively inhibits the elongation of oligonucleotides containing c-Myc promoter G-quadruplex sequence in PCR-stop assays. UV-vis spectroscopic and circular dichroism studies suggest that ActD interacts with c-Myc promoter G-quadruplex via a surface end stacking interaction, inducing a mixed-type conformation of the G-quadruplex. ActD selectively inhibits the cellular growth and synthesis of c-Myc mRNA in Ramos cells having the NHEIII(1) region in the translocated c-Myc gene. In addition, the results of promoter assays using two kinds of NHEIII(1) region mutants and wild-type constructs strongly support the idea that binding of ActD with G-quadruplex formed in the promoter region results in the reporter gene being turned off. Our study reveals a novel mechanism underlying the anticancer activity of ActD, whereby ActD interacts with oncogenic promoter G-quadruplex DNA to repress gene expression.
Kang
Hyun-Jin
HJ
College of Pharmacy, Sungkyunkwan University, Suwon 440-746, Republic of Korea.
Park
Hyun-Ju
HJ
D000903:Antibiotics, Antineoplastic / Q000737:chemistry* / Q000378:metabolism / Q000633:toxicity; D001665:Binding Sites; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D004273:DNA, Neoplasm / Q000737:chemistry* / Q000378:metabolism; D003609:Dactinomycin / Q000737:chemistry* / Q000378:metabolism / Q000633:toxicity; D054856:G-Quadruplexes; D006801:Humans; D009857:Oncogenes; D011401:Promoter Regions, Genetic; D016271:Proto-Oncogene Proteins c-myc / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics; D014158:Transcription, Genetic
D000903:Antibiotics, Antineoplastic; D004273:DNA, Neoplasm; D016271:Proto-Oncogene Proteins c-myc; D003609:Dactinomycin