Molecular mechanisms of histone inheritance during DNA replication

Chromatin is partitioned into functional domains. Nucleosomes within these domains contain specific histone variants and post-translational modifications (PTMs) that modulate chromatin structure and dynamics. During DNA replication, parental nucleosomes are disassembled ahead of the replication fork, followed by their restoration on daughter strands from recycled parental and new histones. Local histone recycling at the replication fork is central to epigenetic inheritance but the molecular mechanisms underlying this process are poorly understood. I have developed a real-time single-molecule imaging platform that allows simultaneous visualisation of parental histones and replication forks as they navigate through the nucleosomal environment of individual DNA molecules in Xenopus egg extracts. Using this approach, I showed that, upon collision with forks, histones can be locally recycled, evicted from the DNA, pushed by forks over tens-of-kilobases and even stall forks. Importantly, I found that free histone concentration is a key modulator of parental histone recycling at the replication fork. I will exploit this novel single-molecule technology, and combine it with biochemical and biophysical methods, to uncover how histone variants and PTMs affect nucleosome dynamics during DNA replication. My work will provide mechanistic insight into replication-coupled histone inheritance and shed light on how chromatin structures are maintained.