Before dividing, a cell must rapidly and accurately replicate its entire genome. Defects in DNA replication can result in a range of defects (collectively termed ‘genome instability’), including mutation and chromosomal rearrangements; these underlie the genesis of cancer and several other human diseases.
DNA replication is intrinsically asymmetric. Only one parental strand at the replication fork can be continuously replicated: the other – the lagging strand – is discontinuously synthesized via the iterative polymerization, processing and ligation of Okazaki fragments. To fully replicate the human genome, a cell must synthesize and process around 20 million Okazaki fragments. We use a combined genetic and genomic approach to define how these intermediates are synthesized and processed in vivo.
We also use Okazaki fragments as a tool to study DNA replication dynamics in the cell. We seek to define what determines the sites of DNA replication initiation, and how the replication machinery overcomes the various obstacles it encounters in the genome.
Finally, we are also interested in DNA damage tolerance and repair. Because ribonucleotides mis-incorporated into the genome during replication are by far the most abundant lesion in DNA, we are particularly interested in ribonucleotide excision repair.
Some examples of specific questions we are currently working on are:
• How does the eukaryotic DNA replication machinery move past (or through) obstacles?
• What defines the sites of replication initiation and termination in human and other eukaryotic genomes?
• How do imbalanced levels of the three replicative DNA polymerases compromise genome integrity?
• How do ribonucleotides in genomic DNA affect cellular physiology, and how are they removed?