title: Conformational variability of recombination R-triplex formed by the mammalian telomeric sequence.
abstract: Alignment of three nucleic acids strands, in which the third strand is identical to one of the DNA duplex strands, occurs in various cellular systems. In the case of telomeric t-loops, recognition between the DNA duplex and the homologous single strand is likely to be mediated by proteins through formation of the transient recombination-type R-triplex. Earlier, using 2-aminopurine as a fluorescent reporting base, we evaluated the thermodynamic characteristics of intramolecular R-triplex formed by a mixed nucleotide sequence. Here, we used this approach to explore a propensity of the telomeric TTAGGG repeat to form the R-triplex. The circular dichroism spectral changes detected upon formation of the R-triplex suggest that this process is accompanied by specific conformational changes in DNA, including a local destabilization of the target duplex next to a GGG run revealed by the fluorescence of the reporting 2-aminopurine base. Surprisingly, stability of the R-triplex formed by telomeric sequence depends strikingly on the counter ion, being higher for Na(+) than for Li(+). Taken together these findings indicate a significant conformational variability of telomeric DNA in the context of recombination-type R-triplex, a phenomenon of possible biological relevance.
authors: a Engelhardt Institute of Molecular Biology, Russian Academy of Sciences , 119991 Moscow , Russia.
authors: Anna K
authors: AK
authors: Shchyolkina
authors: a Engelhardt Institute of Molecular Biology, Russian Academy of Sciences , 119991 Moscow , Russia.
authors: Dmitry N
authors: DN
authors: Kaluzhny
authors: a Engelhardt Institute of Molecular Biology, Russian Academy of Sciences , 119991 Moscow , Russia.
authors: Olga F
authors: OF
authors: Borisova
authors: b Department of Molecular Biology , Max Planck Institute for Biophysical Chemistry , D-37070 Goettingen , Germany.
authors: Donna J
authors: DJ
authors: Arndt-Jovin
authors: b Department of Molecular Biology , Max Planck Institute for Biophysical Chemistry , D-37070 Goettingen , Germany.
authors: Thomas M
authors: TM
authors: Jovin
authors: c Laboratory of Cell Biology , National Cancer Institute, NIH , 20892 Bethesda , MD , USA.
authors: Victor B
authors: VB
authors: Zhurkin
mesh_terms: D001483:Base Sequence; D002942:Circular Dichroism; D004247:DNA / Q000737:chemistry*; D006860:Hydrogen Bonding; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D009841:Oligonucleotides / Q000737:chemistry; D016615:Telomere / Q000737:chemistry* / Q000235:genetics*; D013816:Thermodynamics
chemical_list: D009841:Oligonucleotides; D004247:DNA
keywords: R-triplex; circular dichroism; fluorescence; telomeric DNA; thermodynamic stability