In the Genome Stability Laboratory, we are using yeast, DT40 and human cells to study the DNA damage response (DDR). Our work directly impacts on cancer as abrogation of the DDR is causally implicated in oncogenesis. Furthermore, with the exception of surgery, the vast majority of cancer therapeutic approaches either introduce DNA damage or target the DDR in proliferating cancer cells which have compromised DNA repair. Improved understanding of the DDR will result in improved cancer diagnosis/prognosis and therapeutic interventions.
The DDR is a complex, interacting network of biochemical pathways that ultimately prevents the accumulation of cells with mutations. This response constantly surveys the genome for damage that threatens its stability. Once structural alterations have been sensed there are five broad biological outcomes: 1) DNA repair; 2) transient delays to cell cycle progression (termed checkpoints); 3) a transcriptional programme; 4) programmed cell death (apoptosis) and 5) senescence. Failure to properly integrate these biological responses results in genome instability, which in turn can result in activation of proto-oncogenes or inactivation of tumour suppressors.
Using the genetic tractability of our model systems we ‘knock-out’ (see Figure 1) or ‘knock-down’ genes, as well as ‘knock-in’ either mutations or epitopes that faciliate biochemical (Figure 2) or cell biological approaches (Figure 3). Currently we are focused on proteins required for sensing and transducing the DNA damage signal, including yeast Mec1, Rad9 and Chk1; as well as vertebrate ATM, ATR, BRCA1, and 53BP1. In addition, we have recently used quantitative proteomic (SILAC-assisted mass spectrometry) to characterise the interacting partners of the 53Bp1, Atm and Atr proteins from chicken DT40 cells. Several ‘hits’ from this screening approach and now the subject of further analyses and have been extended to their homologues in human cells. Extrapolation of discoveries made with our model systems to human cells has revealed new activities whose potential as tumour suppressors will be assessed in future work.