Investigating the interaction between PRC2 and G-quadruplex DNA

This is a summer student position supervised by John Houslay in Steve Gamblin's lab.

Introduction to the Science

The Gamblin lab uses biochemical and structural approaches to understand how proteins associated with disease operate. One class of proteins we are particularly interested in are those that regulate gene expression through changes to chromatin at the molecular level.

About the Project

Polycomb repressive complex 2 (PRC2) is a protein complex that helps control which genes are turned off in a cell. It does this by methylating histone H3 at lysine 27 (H3K27). This modification establishes a repressive chromatin state and is essential for cell differentiation and development. The regulation of PRC2 is highly complex and mutations in PRC2 are frequent in many diseases such as cancer. Understanding the basic mechanisms by which PRC2 is regulated is therefore key to the treatment of disease.

One way PRC2 is regulated is through its interaction with RNA. PRC2 can specifically recognise and bind to RNA secondary structures known as G-quadruplexes. These structures are formed by consecutive repeats of guanines and, upon binding PRC2, inhibit its enzymatic activity. To date, work by the Gamblin lab and others has focused on studying this interaction in detail using biochemical and structural methods.

Interestingly, G-quadruplexes can also form in DNA, but whether PRC2 binds these DNA structures has not yet been studied. The proposed project will therefore focus on characterising this interaction in vitro. This will first involve rationally designing G-quadruplex forming DNA sequences and purifying these sequences by chromatography techniques. The binding of G-quadruplex DNA to PRC2 will then be quantitatively measured by biophysical techniques such as fluorescence anisotropy. Finally, the effect of DNA G-quadruplexes on PRC2 enzymatic activity will be compared to that of RNA G-quadruplexes.

Candidate background