title: Conformation and stability of intramolecular telomeric G-quadruplexes: sequence effects in the loops.
abstract: Telomeres are guanine-rich sequences that protect the ends of chromosomes. These regions can fold into G-quadruplex structures and their stabilization by G-quadruplex ligands has been employed as an anticancer strategy. Genetic analysis in human telomeres revealed extensive allelic variation restricted to loop bases, indicating that the variant telomeric sequences maintain the ability to fold into G-quadruplex. To assess the effect of mutations in loop bases on G-quadruplex folding and stability, we performed a comprehensive analysis of mutant telomeric sequences by spectroscopic techniques, molecular dynamics simulations and gel electrophoresis. We found that when the first position in the loop was mutated from T to C or A the resulting structure adopted a less stable antiparallel topology; when the second position was mutated to C or A, lower thermal stability and no evident conformational change were observed; in contrast, substitution of the third position from A to C induced a more stable and original hybrid conformation, while mutation to T did not significantly affect G-quadruplex topology and stability. Our results indicate that allelic variations generate G-quadruplex telomeric structures with variable conformation and stability. This aspect needs to be taken into account when designing new potential anticancer molecules.
authors.affiliation: Department of Molecular Medicine, University of Padua, Padua, Italy.
authors.forename: Giovanna
authors.initials: G
authors.lastname: Sattin
authors.affiliation: Dipartimento di Scienze della Salute, Università "Magna Græcia" di Catanzaro, Catanzaro, Italy.
authors.forename: Anna
authors.initials: A
authors.lastname: Artese
authors.affiliation: Department of Molecular Medicine, University of Padua, Padua, Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Nadai
authors.affiliation: Dipartimento di Scienze della Salute, Università "Magna Græcia" di Catanzaro, Catanzaro, Italy.
authors.forename: Giosuè
authors.initials: G
authors.lastname: Costa
authors.affiliation: Dipartimento di Scienze della Salute, Università "Magna Græcia" di Catanzaro, Catanzaro, Italy.
authors.forename: Lucia
authors.initials: L
authors.lastname: Parrotta
authors.affiliation: Dipartimento di Scienze della Salute, Università "Magna Græcia" di Catanzaro, Catanzaro, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Alcaro
authors.affiliation: Department of Pharmaceutical and Pharmacological Sciences, University of Padua, Padua, Italy.
authors.forename: Manlio
authors.initials: M
authors.lastname: Palumbo
authors.affiliation: Department of Molecular Medicine, University of Padua, Padua, Italy.
authors.forename: Sara N
authors.initials: SN
authors.lastname: Richter
mesh_terms: D001483:Base Sequence; D054856:G-Quadruplexes; D006801:Humans; D056004:Molecular Dynamics Simulation; D009154:Mutation; D009841:Oligonucleotides / Q000737:chemistry / Q000235:genetics; D016615:Telomere / Q000737:chemistry* / Q000235:genetics*; D044366:Transition Temperature
chemical_list: D009841:Oligonucleotides