title: Modulation of c-myc transcription by triple helix formation.
abstract: The human c-myc oncogene promoter was used as a model with which to study the mechanism of action of oligodeoxyribonucleotides targeted to a gene regulatory region. The nuclease-hypersensitive element, NHE, lying -115 bp from the P1 promoter of the human c-myc gene, is known to be required in cis for transcription of the gene from both P1 and P2 promoters (Fig. 1). Inhibition of c-myc transcription by an oligonucleotide designed to bind to NHE by triplex formation has been observed in a cell-free transcription assay. Using a reconstituted transcription system with the semipurified PuF transcription factor whose site of interaction resides within the NHE, it is shown here that the oligonucleotide inhibits PuF-mediated transcription. These findings, together with data presented elsewhere showing that: (1) PU1 binds to cloned DNA fragments to form a colinear triplex; (2) PU1 inhibits transcription in nuclear extracts; (3) triple helix formation inhibits the binding of PuF to its target NHE element in an in vitro binding competition assay (E. Postel, R. Durland, and M. Hogan, submitted); (4) triplex formation at the NHE target site can occur in living HeLa cells treated with the triplex-forming PU1 oligomer, and (5) c-myc mRNA synthesis in these treated cells is repressed, clearly support the proposed model in which the oligonucleotide targeted against the c-myc NHE promoter region binds to form a triplex, thereby blocking access to the regulatory protein PuF. This results in promoter-sensitive repression of transcriptional activation of the c-myc gene. The potential for manipulation of gene expression by oligonucleotides targeted to a DNA sequence of the c-myc oncogene promoter and other gene promoters is clear.
authors.affiliation: Department of Molecular Biology, Princeton University, New Jersey 08546-1014.
authors.forename: E H
authors.initials: EH
authors.lastname: Postel
mesh_terms: D001483:Base Sequence; D004247:DNA; D016259:Genes, myc / Q000235:genetics*; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009838:Oligodeoxyribonucleotides / Q000494:pharmacology*; D016376:Oligonucleotides, Antisense / Q000494:pharmacology*; D011401:Promoter Regions, Genetic / Q000235:genetics*; D012333:RNA, Messenger / Q000032:analysis; D014158:Transcription, Genetic / Q000187:drug effects*
chemical_list: D009838:Oligodeoxyribonucleotides; D016376:Oligonucleotides, Antisense; D012333:RNA, Messenger; C051802:triplex DNA; D004247:DNA