Balasubramanian Group

G quadruplexes

Nucleic acids are highly flexible molecules than can adopt different conformational structures. While in living systems DNA is largely double helical and RNA is single stranded, guanine-rich sequences can exist in alternative structural forms known as G-quadruplex nucleic acids. We are investigating the functional relevance of a quadruple helical form of nucleic acids and its implication for the biology of nucleic acids. The G-quadruplex hypothesis is of fundamental importance to life and may well hold the key to new therapeutic approaches in numerous areas of human disease that include cancer.

Specific mechanisms under investigation include: DNA G-quadruplex formation at the telomeres and their importance for genomic stability and replication; DNA G-quadruplexes in gene promoters and the regulation of transcription; RNA G-quadruplexes in the untranslated regions of mRNA and the control of protein synthesis (translation).

As part of our studies, we are synthesising new molecules that stabilise the nucleic acid quadruple helix and interfere with specific cellular processes. We make extensive use of biophysical methods (NMR, UV, CD and fluorescence spectroscopy) to study quadruplexes and their interactions with molecules. We are also employing computational methods (bioinformatics) and genomics to explore quadruplexes in genomes.

Epigenetics and Modified Bases

We are interested in understanding chemical modifications to DNA and the effect of such changes to the structure and function of DNA. DNA is made up of four bases – cytosine, guanine, adenine and thymine. However, these bases can naturally undergo chemical modification leading to new bases. Changing one of the bases in a strand of DNA in this way alters its property and function by controlling how the sequence is interpreted. This can affect how genes are switched on and off in different cell types, tissues and organs. 

The modified base 5-methylcytosine (5mC) is a well-known epigenetic mark that can regulate transcription of the genome. Since 2009 three further modified bases have been detected in the mammalian genome. These are the TET-enzyme generated bases; 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC) and 5-carboxylcytosine (5caC). The presence of these modifications opens up questions as to their function in normal cellular biology and disease states. 

We are developing chemical tools and genomic methods to map and elucidate the function of these modified bases. 

We are also exploring the molecular basis for their involvement in biological mechanisms.  Part of this work exploits state of the art genomics technologies. We have already created methods to quantitatively sequence 5mC, 5hmC and 5fC at single-base resolution. Such tools allow much more accurate study of these epigenetic marks. 

The scope of our work will also include the identification, mapping, and elucidation of the biological function of other base modifications in the DNA and RNA of various organisms.