Investigating the factors that influence genome stability when replication forks encounter single-strand DNA breaks and protein roadblocks

DNA replication is fundamental to the propagation of life.

It is performed by complex protein machines, which are assembled onto DNA at chromosomal sites known as replication origins. These machines unwind the DNA double helix to form "fork" structures, at which the copying occurs. In eukaryotes, replication commences with the firing of origins during S-phase of the cell cycle.

Upon firing, each origin releases a pair of "replication forks" that travel in opposite directions away from their site of initiation. DNA replication is completed when forks from adjacent origins merge.

This potentially seamless pattern of replication initiation, elongation and termination is disrupted by different types of single-strand DNA breaks (SSBs) and protein-DNA complexes (PDCs), which block replication fork progression. Replication fork blockage can cause the replication machine to disassemble and the fork to break.

It can also cause under-replication of DNA and consequent problems with chromosome segregation during cell division.

These potential outcomes pose a major threat to genome stability, which is mitigated by pathways that variously protect, repair and restart blocked forks.

However, these pathways are not risk-free and can also cause mutations and genome rearrangements, which may promote ageing and age-related diseases such as cancer.

The aim of this project is to determine how the cellular response to replication fork blockage is affected by the nature and context of the SSB/PDC, and how this in turn influences the risk of mutation and genome rearrangement.

We will also discover key factors that direct the processing of blocked forks down safer routes and enable forks converged at PDCs to be resolved.

As genome deterioration is thought to be a key driver of the ageing process, a better understanding of its root causes, and factors that slow its progress, will ultimately guide the development of new strategies to maximise our potential for healthy ageing.