FORMATION OF A HAIRPIN STRUCTURE BY TELOMERE 3 OVERHANG

Abstract

The telomeres of most eukaryotes contain tandemly-repeated DNA sequences, with a cluster of G residues on one strand. Recent studies showed that the Oxytricha telomeric DNA oligonucleotide, d(G(4)T(4)G(4)), dimerizes to form a quadruplex in the presence of Na+ or K+. We have observed that the oligonucleotide d(G(4)T(4)G(4)) does not dimerize in the presence of Li+ ion at low sample concentrations. In the monomeric state, this molecule forms a simple foldback hairpin structure containing G.G reverse Hoogsteen basepairs in the stem region. This hairpin structure has a thermal stability which is well reconciled with telomere functions in vivo.