Structure:Function Correlation in the Human DNA Repair Factor CtIP

Our bodies are composed of billions of cells of many different types that perform all the tasks we need to survive. Every day our healthy cells are constantly being challenged by damage to their DNA. As DNA contains all the information necessary for life, it is crucial that its structure is maintained.

DNA damage causes mistakes known as mutations and if these are not repaired properly it can eventually lead to diseases such as cancer. We are interested in a particularly harmful type of damage called double-strand breaks (DSBs), where the DNA is physically broken by damaging agents which come from outside the cell or simply as a result of the many complex processes that occur normally on DNA.

When a DSB occurs, it is crucial that the ends are joined back together again without errors. This process requires many different proteins which collaborate to bridge the DNA ends, trim away any bulky adducts at the DNA ends that have arisen when it was damaged, and then unwind the DNA double-helix while cleaving one of the DNA strands. This exposes the genetic code surrounding the damage, allowing the cell to find an equivalent undamaged portion of DNA to use as a template for repair.

The overall scheme for this process, which is called Homologous Recombination, is complicated but has been well-studied. However, there is a lack of fine detail in the understanding of the way in which the individual proteins that act as repair factors work together, and this negatively impacts on our ability to treat diseases caused by defective DNA repair pathways, as well as to safely apply new methods for editing human genomes.

We are especially interested in a protein called CtIP, which is especially important as it appears to act as a structural hub for repair of broken DNA by co-ordinating the broken DNA ends with many of the other factors required to fix them. Moreover, when CtIP is not working properly, it has been implicated in cancer and the rare human diseases Seckel and Jawad syndromes which cause dwarfism and neurological disorders.

Despite its significance, we know very little indeed about the architecture of the CtIP protein, how it interacts with DNA and other proteins, and what is wrong with CtIP in the disease state. In this project, we have assembled a team of interdisciplinary researchers to apply a range of techniques in biophysics, biochemistry and cell biology to piece together the relationship between the structure and cellular function of this important protein and the complexes it forms with DNA and other partners.

This new knowledge will dramatically improve our understanding of human DNA break repair with wide ranging implications for the diagnosis and treatment of cancer and other diseases, as well as the further refinement of modern gene editing technology.