Abstract

DNA double-strand breaks (DSB) is one of the most severe types of DNA damage and cells have evolved a range of repair pathways including homologous recombination to deal with DSB . In eukaryotes, additional complications are due to the inaccessibility of the damaged sites, which are wrapped in nucleosomes and chromatin. Unsurprisingly, a large number of proteins and macromolecular complexes, including many major tumour suppressors such as ATM , ATR, BRCA1 and BRCA2 , play central roles in homologous recombination. ATM (yeast Tel1) and ATR (yeast Mec1) are involved in damage signalling to coordinate the repair events with cell cycle progression whereas BRCA1 and BRCA2 are directly involved in recruiting and assembly of Rad51 recombinase. A number of chromatin remodellers including the multi-subunit INO80 complex have also been implicated in this pathway although their precise roles are unclear. Apart from these large proteins and complexes, a central player is the heterotrimer protein RPA , which binds to single stranded DNA , acting as a crucial intermediate in homologous recombination and replication. Our research focuses on elucidating the structures and mechanisms of the major macromolecular complexes involved in this pathway, primarily using cryo electron microscopy techniques. In this seminar, I will discuss our recent progress on a number of key components and our current mechanistic understanding of these proteins and macromolecular complexes.