Current Research:
Many routinely used anti-cancer drugs act by generating a specific form of DNA damage, interstrand crosslinks (ICLs), that kills tumour cells by inhibiting essential processes such as DNA replication and transcription. An enhanced ability to repair and tolerate this type of damage is implicated in tumour resistance to crosslinking agents. Therefore, a better understanding of the repair and tolerance mechanisms acting on ICLs might allow us to improve chemotherapy regimens that rely on crosslinking drugs, perhaps by introducing inhibitors of key repair enzymes.

Using yeast as a model organism we have shown that two major DNA repair pathways collaborate in the repair of ICLs, nucleotide excision repair and homologous recombination. NER is required to incise and uncouple DNA interstrand crosslinks, initiating ICL repair, whereas homologous recombination acts downstream from this and utilises DNA double-strand break intermediates. However, many the biochemical details of these events are still poorly understood.

Future projects:
Using defined synthetic DNA substrates containing site-specific ICLs we hope to reconstitute key events during ICL repair with cell extracts and purified repair proteins. We also have a particular interest in the Snm1 family of proteins in this process because snm1 defective cells are sensitive to cross-linking agents, but not other forms of DNA damage. This approach, coupled with continued genetic analysis of ICL repair events, should shed light on many of the details of this complex DNA repair pathway.

An additional interest is a recently identified role for the RAD6-RAD18 pathway in the excision repair of DNA adducts located in the minor groove of DNA. We intend to explore the DNA structural requirements for this, and address the biochemical role of Rad6-Rad18 and Rad5 in these reactions.