Understanding the biological role of the i-motif

The DNA i-motif is an important biological target which has recently been shown to form inside the nucleus of human cells. Current understanding of this structure is limited as it has received little research focus over the last 30 years, primarily because it was thought it couldn’t exist within biological environment. We have recently discovered that the DNA sequence requirements used to determine if an i-motif will form are not fully inclusive and exclude physiologically stable i-motif forming sequences. We aim to redefine the sequence requirements for i-motif formation, linking this to the structural basis for the effect of sequence on the formation and stability of i-motif structures.

The i-motif is a four stranded DNA structure formed by cytosine rich sequences of DNA containing protonated-cytosine: cytosine (C+:C) bases pairs that form the core of the structure, leading to the belief that the i-motif would only form under acidic conditions. However, it is now clear that the i-motif can transiently form under physiological conditions and its formation is dependent on DNA sequence.

In this project we will:

use a variety of biophysical techniques, including UV and CD spectroscopy to examine the sequence requirements of i-motif formation,

probe the effect of sequence on the stability of the structure,

investigate the effect of environmental factors, such as pH, ionic strength and molecular crowding on formation and stability.

Informal enquires should be directed to Dr John Brazier (j.a.brazier@reading.ac.uk)