Mechanism of Chromatin Replication

Each time a human cell divides, it must make an exact copy of its 46 chromosomes. This requires precise duplication of ~6 billion base pairs of genomic DNA and all its associated proteins. Mistakes in this process can lead to developmental defects and cancer. Chromatin is packaged as nucleosomes comprising 147bp of DNA wrapped around a core of eight histone proteins.

The nucleosome is a stable structure which must be disrupted each time the double helix is accessed during replication. ‘Epigenetic’ information in the form of covalent histone modifications must be re-established on both daughter strands immediately behind the replication fork.

Inheritance of parental histones with their covalent marks must be coordinated with deposition of new histones into nucleosomes. And repressive heterochromatin must be replicated and immediately re-established after replication.

Our goal is to achieve a deep understanding of how DNA replication is coordinated with the disassembly and reassembly of chromatin to ensure accurate chromosome duplication.

We will use in vitro reconstitution of chromatin replication along with molecular genetics and structural biology to:•Generate a molecular view of how the budding yeast replication machinery, with other key factors, disrupts parental nucleosomes during replication. •Determine how parental nucleosomes are transferred to the nascent daughter strands. •Understand how deposition of new histones is coordinated with the inheritance of parental histones. •Characterise how budding yeast heterochromatin is disrupted and re-established during replication. •Begin studying this process using human proteins, focussing on areas where human replication mechanisms diverge from yeast.

This work will underpin our long-term goal of reconstituting functional chromosomes from defined components to understand how DNA replication interacts with gene expression, DNA repair and chromosome segregation.