Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, Australia; Illawara Health and Medical Research Institute, Wollongong, Australia
Aaron Lavel Moye
Children’s Medical Research Institute, University of Sydney, Westmead, Australia
School of Science, College of Science, Engineering and Health, RMIT University, Melbourne, Australia
Monica L Birrento
Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, Australia; Illawara Health and Medical Research Institute, Wollongong, Australia
Siritron Samosorn
Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Srinakharinwirot University, Bangkok, Thailand
Kamthorn Intharapichai
Department of Biobased Materials Science, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto, Japan
Christopher G Tomlinson
Children’s Medical Research Institute, University of Sydney, Westmead, Australia
Marie-Paule Teulade-Fichou
Institut Curie, PSL Research University, Orsay, France; Université Paris Sud, Université Paris-Saclay, Orsay, France
Instituto de Química Física ‘Rocasolano’, CSIC, Madrid, Spain
Jennifer L Beck
Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, Australia; Illawara Health and Medical Research Institute, Wollongong, Australia
Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, Australia; Illawara Health and Medical Research Institute, Wollongong, Australia
Telomeric G-quadruplexes (G4) were long believed to form a protective structure at telomeres, preventing their extension by the ribonucleoprotein telomerase. Contrary to this belief, we have previously demonstrated that parallel-stranded conformations of telomeric G4 can be extended by human and ciliate telomerase. However, a mechanistic understanding of the interaction of telomerase with structured DNA remained elusive. Here, we use single-molecule fluorescence resonance energy transfer (smFRET) microscopy and bulk-phase enzymology to propose a mechanism for the resolution and extension of parallel G4 by telomerase. Binding is initiated by the RNA template of telomerase interacting with the G-quadruplex; nucleotide addition then proceeds to the end of the RNA template. It is only through the large conformational change of translocation following synthesis that the G-quadruplex structure is completely unfolded to a linear product. Surprisingly, parallel G4 stabilization with either small molecule ligands or by chemical modification does not always inhibit G4 unfolding and extension by telomerase. These data reveal that telomerase is a parallel G-quadruplex resolvase.
