Effect of a Single Repeat Sequence of the Human Telomere d(TTAGGG) on Structure of Single-Stranded Telomeric DNA dAGGG(TTAGGG)_6

The structures of human telomeric DNA have received much attention due to its significant biological importance. Most studies have focused on G-quadruplex structure formed by short telomeric DNA sequence, but little is known about the structures of long single-stranded telomeric DNAs. Here, we investigated the structure of DNA with a long sequence of dAGGG(TTAGGG)_6 (G_6-DNA) and the effect of a single repeat sequence d(TTAGGG) (G_01-DNA) on the structure of G_6-DNA using sedimentation velocity technique, polyacrylamide gel electrophoresis, circular dichroism spectroscopy, and UV melting experiments. The results suggest that the G_6-DNA can form dimers in aqueous solutions and G_01-DNA can form additional G-quadruplex structures by binding to G_6-DNA. However, G_01-DNA has no effect on the structure of DNA with a sequence of dAGGG(TTAGGG)_3 (G_3-DNA). Our study provides new insights into the structure polymorphism of long human single-stranded telomeric DNA.