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Publication Abstract from PubMed

CCG triplet repeats can fold into tetraplex structures, which are associated with the expansion of (CCG)n trinucleotide sequences in certain neurological diseases. These structures are stabilized by intertwining i-motifs. However, the structural basis for tetraplex i-motif formation in CCG triplet repeats remains largely unknown. We report the first crystal structure of a CCG-repeat sequence, which shows that two dT(CCG)3 A strands can associate to form a tetraplex structure with an i-motif core containing four C:C(+) pairs flanked by two G:G homopurine base pairs as a structural motif. The tetraplex core is attached to a short parallel-stranded duplex. Each hairpin itself contains a central CCG loop in which the nucleotides are flipped out and stabilized by stacking interactions. The helical twists between adjacent cytosine residues of this structure in the i-motif core have an average value of 30 degrees , which is greater than those previously reported for i-motif structures.

Structural basis for the identification of an i-motif tetraplex core with a parallel-duplex junction as a structural motif in CCG triplet repeats.,Chen YW, Jhan CR, Neidle S, Hou MH Angew Chem Int Ed Engl. 2014 Sep 26;53(40):10682-6. doi: 10.1002/anie.201405637. , Epub 2014 Aug 19. PMID:25139267^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.