Dr Chris West
I am a BBSRC David Phillips Research Fellow and research in my laboratory is focused on the pathways of DNA repair in plant cells using the model plant Arabidopsis thaliana. In all organisms, the genome is constantly under attack from environmental factors and by endogenous metabolic by-products. DNA double strand breaks (DSB) are one of the most cytotoxic forms of DNA damage that can occur in the cell. Failure to recognise and repair a single DSB can lead to cell death. Powerful DNA repair and cell cycle checkpoint mechanisms have evolved to minimise the detrimental effects of these breaks in organisms. In plants and animals the main DSB repair pathway is the direct end-to-end rejoining of the break in a process termed non-homologous end joining (NHEJ). This process is inherently error prone and often results in small mutations at the repair site as the DNA ends may be ‘polished’ prior to rejoining.
An alternative pathway for DSB repair relies on recombination of the damaged region with a homologous sequence in genome (often a sister chromatid or homologous chromosome). Homologous recombination (HR) is the main DSB repair pathway in micro-organisms and is frequent in the moss Physcomitrella patens. The great advantage of high levels of HR is that it allows molecular biologists to target transgenic DNA to particular sites in the genomes of these organisms, allowing high precision genetic modification (gene targeting). In contrast, in higher plants gene targeting events are very rare, accounting for approximately 1 in 104 transformation events depending on species. The development of gene targeting technologies in important crop species will result in more stable and predictable levels of trangene expression and allow subtle changes in host genes that confer agronomically important traits. In addition, gene targeting technologies would benefit the plant research community by facilitating functional analysis of novel genes in these crops.
I have characterised the main components of the Arabidopsis NHEJ pathway and I am using a combination of biochemical, molecular and cell biology techniques to obtain a detailed understanding of the mechanisms of DSB repair in plants. Current projects will establish the protein(s) responsible for the initial recognition of the DSB and subsequent recruitment of repair factors, a process that is key in determining which pathway of DSB repair is used. DSB detection may also result in activation of cell cycle checkpoints and current studies are investigating the protein complexes responsible for DNA damage signalling in Arabidopsis.