The beta subunit of Oxytricha telomere-binding protein promotes G-quartet formation by telomeric DNA.
Telomeres, the ends of linear chromosomes, typically consist of tandem repeats of simple G-rich sequences. At high concentrations, single-stranded telomeric DNA can form dimers and tetramers involving G-quartets. We show that under physiological conditions, the beta subunit of the Oxytricha telomere-binding protein greatly accelerates G-quartet formation. The reaction occurs with oligonucleotides ending in the Oxytricha (T4G4T4G4) and Tetrahymena (T2G4T2G4) telomeric sequences; the sequence preceding these telomeric repeats can be nontelomeric, single-, or double-stranded. Protein deletion analysis indicates that the carboxy-terminal highly basic domain of the beta subunit, which is dispensible for telomeric complex formation, is sufficient for mediating G-quartet formation. The finding that a telomeric protein acts as a molecular chaperone for G-quartet formation provides a strong argument that such DNA structures exist in vivo at chromosome telomeres.
Department of Chemistry and Biochemistry, Howard Hughes Medical Institute, University of Colorado, Boulder 80309-0215.
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D000818:Animals; D001483:Base Sequence; D016054:DNA, Protozoan / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D006860:Hydrogen Bonding; D046911:Macromolecular Substances; D008745:Methylation; D008961:Models, Structural; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides / Q000138:chemical synthesis / Q000378:metabolism; D016813:Oxytricha / Q000235:genetics / Q000378:metabolism*; D016615:Telomere / Q000378:metabolism*
D016054:DNA, Protozoan; D004268:DNA-Binding Proteins; D046911:Macromolecular Substances; D009838:Oligodeoxyribonucleotides