6m5j
U shaped head to head four-way junction in d(TTCTGCTGCTGAA/TTCTGCAGCTGAA) sequence
Structural highlights
Publication Abstract from PubMedThe potent DNA-binding compound triaminotriazine-acridine conjugate (Z1) functions by targeting T:T mismatches in CTG trinucleotide repeats that are responsible for causing neurological diseases such as myotonic dystrophy type 1, but its binding mechanism remains unclear. We solved a crystal structure of Z1 in a complex with DNA containing three consecutive CTG repeats with three T:T mismatches. Crystallographic studies revealed that direct intercalation of two Z1 molecules at both ends of the CTG repeat induces thymine base flipping and DNA backbone deformation to form a four-way junction. The core of the complex unexpectedly adopts a U-shaped head-to-head topology to form a crossover of each chain at the junction site. The crossover junction is held together by two stacked G:C pairs at the central core that rotate with respect to each other in an X-shape to form two nonplanar minor-groove-aligned G.C.G.C tetrads. Two stacked G:C pairs on both sides of the center core are involved in the formation of pseudo-continuous duplex DNA. Four metal-mediated base pairs are observed between the N7 atoms of G and Co(II), an interaction that strongly preserves the central junction site. Beyond revealing a new type of ligand-induced, four-way junction, these observations enhance our understanding of the specific supramolecular chemistry of Z1 that is essential for the formation of a noncanonical DNA superstructure. The structural features described here serve as a foundation for the design of new sequence-specific ligands targeting mismatches in the repeat-associated structures. Structural Basis for Targeting T:T Mismatch with Triaminotriazine-Acridine Conjugate Induces a U-Shaped Head-to-Head Four-Way Junction in CTG Repeat DNA.,Chien CM, Wu PC, Satange R, Chang CC, Lai ZL, Hagler LD, Zimmerman SC, Hou MH J Am Chem Soc. 2020 Jun 24;142(25):11165-11172. doi: 10.1021/jacs.0c03591. Epub , 2020 Jun 16. PMID:32478511[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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