6XT7

Tel25 Hybrid Four-quartet G-quadruplex with K+

Summary for 6XT7

• Entry DOI: 10.2210/pdb6xt7/pdb
• Descriptor: DNA (25-MER), MAGNESIUM ION, POTASSIUM ION, ... (5 entities in total)
• Functional Keywords: g-quadruplex, hybrid, four-quartets, lateral loops, propeller loop, dna
• Biological source: Tetrahymena thermophila
• Total number of polymer chains: 4
• Total formula weight: 32960.02

Authors

Yatsunyk, L.A.,McCarthy, S.E. (deposition date: 2020-07-17, release date: 2020-12-30, Last modification date: 2023-10-25)

Primary citation

Beseiso, D.,Chen, E.V.,McCarthy, S.E.,Martin, K.N.,Gallagher, E.P.,Miao, J.,Yatsunyk, L.A.
The first crystal structures of hybrid and parallel four-tetrad intramolecular G-quadruplexes.
Nucleic Acids Res., 50:2959-2972, 2022

PubMed Abstract: G-quadruplexes (GQs) are non-canonical DNA structures composed of stacks of stabilized G-tetrads. GQs play an important role in a variety of biological processes and may form at telomeres and oncogene promoters among other genomic locations. Here, we investigate nine variants of telomeric DNA from Tetrahymena thermophila with the repeat (TTGGGG)n. Biophysical data indicate that the sequences fold into stable four-tetrad GQs which adopt multiple conformations according to native PAGE. Excitingly, we solved the crystal structure of two variants, TET25 and TET26. The two variants differ by the presence of a 3'-T yet adopt different GQ conformations. TET25 forms a hybrid [3 + 1] GQ and exhibits a rare 5'-top snapback feature. Consequently, TET25 contains four loops: three lateral (TT, TT, and GTT) and one propeller (TT). TET26 folds into a parallel GQ with three TT propeller loops. To the best of our knowledge, TET25 and TET26 are the first reported hybrid and parallel four-tetrad unimolecular GQ structures. The results presented here expand the repertoire of available GQ structures and provide insight into the intricacy and plasticity of the 3D architecture adopted by telomeric repeats from T. thermophila and GQs in general.

PubMed: 35212369
DOI: 10.1093/nar/gkac091

Experimental method

X-RAY DIFFRACTION (1.56 Å)