title: HRAS is silenced by two neighboring G-quadruplexes and activated by MAZ, a zinc-finger transcription factor with DNA unfolding property.
abstract: The HRAS promoter contains immediately upstream of the transcription start site two neighboring G-elements, each capable of folding into a G-quadruplex structure. We have previously found that these G-quadruplexes bind to the zinc-finger transcription factors MAZ and Sp1. In the present study we have examined the interaction between the HRAS promoter and MAZ, demonstrating for the first time that the protein unfolds the G-quadruplex structures. We also demonstrate that MAZ-GST, in the presence of the complementary strands, promotes a rapid transformation of the two HRAS quadruplexes into duplexes. By a mutational analysis of the HRAS G-elements, we dissected the MAZ-binding sites from the quadruplex-forming motifs, finding that the two neighboring G-quadruplexes bring about a dramatic repression of transcription, in a synergistic manner. We also discovered that the two G-quadruplexes are strong targets for small anticancer molecules. We found that a cell-penetrating anthratiophenedione (ATPD-1), which binds tightly to the G-quadruplexes (ΔT > 15°C), promotes the total extinction of HRAS transcription. In contrast, when one of the two G-quadruplexes was abrogated by point mutations, ATPD-1 repressed transcription by only 50%. Our study provides relevant information for the rationale design of targeted therapy drugs specific for the HRAS oncogene.
authors.affiliation: Department of Medical and Biological Sciences, School of Medicine, P.le Kolbe 4, 33100 Udine, Italy.
authors.forename: Susanna
authors.initials: S
authors.lastname: Cogoi
authors.affiliation: Gause Institute of New Antibiotics, Russian Academy of Medical Sciences, B. Pirogovskaya, 11, Moscow 119021, Russia Mendeleyev University of Chemical Technology, 9 Miusskaya Square, Moscow 125190, Russia.
authors.forename: Andrey E
authors.initials: AE
authors.lastname: Shchekotikhin
authors.affiliation: Department of Medical and Biological Sciences, School of Medicine, P.le Kolbe 4, 33100 Udine, Italy luigi.xodo@uniud.it.
authors.forename: Luigi E
authors.initials: LE
authors.lastname: Xodo
mesh_terms: D045744:Cell Line, Tumor; D004247:DNA / Q000737:chemistry / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D054856:G-Quadruplexes; D015972:Gene Expression Regulation, Neoplastic; D020868:Gene Silencing; D006801:Humans; D011401:Promoter Regions, Genetic; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics*; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation; D001749:Urinary Bladder Neoplasms / Q000235:genetics
chemical_list: D004268:DNA-Binding Proteins; D014157:Transcription Factors; C076035:c-MYC-associated zinc finger protein; D004247:DNA; C501009:HRAS protein, human; D016283:Proto-Oncogene Proteins p21(ras)