The structure of an endogenous Drosophila centromere reveals the prevalence of tandemly repeated sequences able to form i-motifs.
Centromeres are the chromosomal loci at which spindle microtubules attach to mediate chromosome segregation during mitosis and meiosis. In most eukaryotes, centromeres are made up of highly repetitive DNA sequences (satellite DNA) interspersed with middle repetitive DNA sequences (transposable elements). Despite the efforts to establish complete genomic sequences of eukaryotic organisms, the so-called 'finished' genomes are not actually complete because the centromeres have not been assembled due to the intrinsic difficulties in constructing both physical maps and complete sequence assemblies of long stretches of tandemly repetitive DNA. Here we show the first molecular structure of an endogenous Drosophila centromere and the ability of the C-rich dodeca satellite strand to form dimeric i-motifs. The finding of i-motif structures in simple and complex centromeric satellite DNAs leads us to suggest that these centromeric sequences may have been selected not by their primary sequence but by their ability to form noncanonical secondary structures.
Centro de Biología Molecular "Severo Ochoa" (CSIC-UAM), Universidad Autónoma de Madrid, Nicolás Cabrera 1, 28049 Madrid, Spain.|Instituto de Química Física Rocasolano, CSIC, Serrano 119, 28006 Madrid, Spain.
Miguel
M
Garavís
Centro de Biología Molecular "Severo Ochoa" (CSIC-UAM), Universidad Autónoma de Madrid, Nicolás Cabrera 1, 28049 Madrid, Spain.
María
M
Méndez-Lago
Univ. Bordeaux, ARNA Laboratory, IECB, 2 rue Robert Escarpit, F-33600 Pessac, France.|Inserm ARNA Laboratory, 146 rue Leo Saignat, F-33000 Bordeaux, France.
Valérie
V
Gabelica
The Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, United Kingdom.
Siobhan L
SL
Whitehead
Instituto de Química Física Rocasolano, CSIC, Serrano 119, 28006 Madrid, Spain.
Carlos
C
González
Centro de Biología Molecular "Severo Ochoa" (CSIC-UAM), Universidad Autónoma de Madrid, Nicolás Cabrera 1, 28049 Madrid, Spain.
Alfredo
A
Villasante
D000818:Animals; D020029:Base Pairing; D001483:Base Sequence; D002503:Centromere / Q000235:genetics*; D059006:Chromosomes, Insect / Q000235:genetics; D004276:DNA, Satellite / Q000235:genetics; D019281:Dimerization; D004331:Drosophila melanogaster / Q000235:genetics*; D059372:Nucleotide Motifs / Q000235:genetics*; D020080:Tandem Repeat Sequences / Q000235:genetics*
D004276:DNA, Satellite