Centromeric Alpha‐Satellite DNA Adopts Dimeric i‐Motif Structures Capped by AT Hoogsteen Base Pairs. Issue 27 (27th May 2015)

• Record Type: Journal Article
• Authors: Garavís, Miguel; Escaja, Núria; Gabelica, Valérie; Villasante, Alfredo; González, Carlos
• Is Part Of: Chemistry. Volume 21:Issue 27(2015)
• Page Start: 9816
• Page End: 9824
• Publication Date: 2015-05-27
• Subjects: Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201500448
• Languages: English
• ISSNs: 0947-6539

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>Human centromeric alpha‐satellite DNA is composed of tandem arrays of two types of 171 bp monomers; type A and type B. The differences between these types are concentrated in a 17 bp region of the monomer called the A/B box. Here, we have determined the solution structure of the C‐rich strand of the two main variants of the human alpha‐satellite A box. We show that, under acidic conditions, the C‐rich strands of two A boxes self‐recognize and form a head‐to‐tail dimeric i‐motif stabilized by four intercalated hemi‐protonated C:C⁺ base pairs. Interestingly, the stack of C:C⁺ base pairs is capped by T:T and Hoogsteen A:T base pairs. The two main variants of the A box adopt a similar three‐dimensional structure, although the residues involved in the formation of the i‐motif core are different in each case. Together with previous studies showing that the B box (known as the CENP‐B box) also forms dimeric i‐motif structures, our finding of this non‐canonical structure in the A box shows that centromeric alpha satellites in all human chromosomes are able to form i‐motifs, which consequently raises the possibility that these structures may play a role in the structural organization of the centromere.</p> </abstract>