Affiliation:
1. Instituto de Biología Molecular y Celular de Rosario (IBR), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) - Área Biología General, Dpto. de Ciencias Biológicas, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 531, S2002LRK Rosario, Argentina
Abstract
G-rich sequences that contain stretches of tandem guanines can form four-stranded, intramolecular stable DNA structures called G-quadruplexes (termed G4s). Regulation of the equilibrium between single-stranded and G4 DNA in promoter regions is essential for control of gene expression in the cell. G4s are highly stable structures; however, their folding kinetics are slow under physiological conditions. CNBP (cellular nucleic-acid-binding protein) is a nucleic acid chaperone that binds the G4-forming G-rich sequence located within the NHE (nuclease hypersensitivity element) III of the c-Myc proto-oncogene promoter. Several reports have demonstrated that CNBP enhances the transcription of c-Myc in vitro and in vivo; however, none of these reports have assessed the molecular mechanisms responsible for this control. In the present study, by means of Taq polymerase stop assays, electrophoretic mobility-shift assays and CD spectroscopy, we show that CNBP promotes the formation of parallel G4s to the detriment of anti-parallel G4s, and its nucleic acid chaperone activity is required for this effect. These findings are the first to implicate CNBP as a G4-folding modulator and, furthermore, assign CNBP a novel mode-of-action during c-Myc transcriptional regulation.
Subject
Cell Biology,Molecular Biology,Biochemistry
Cited by
50 articles.
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