Identification of novel pathways involved in heterochromatin establishment and maintenance

This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonChromatin organization and dynamics is crucial for many aspects of cell biology. Heterochromatin, tightly packed DNA, is established in early development through controlled epigenetic processes and needs to be maintained throughout cell generations to ensure proper gene expression and cell function. Heterochromatin protein 1 (HP1) is a highly conserved protein that has been used as a marker for heterochromatin, as by binding to di- and tri-methylated histone H3K9, regulates heterochromatin structure, gene expression, DNA replication, DNA repair, cell cycle, cell differentiation and development. Beside phosphorylations of Histone H3 Ser10 that has been shown to modulate HP1α binding to H3K9me3, several studies have also highlighted the importance of HP1α phosphorylations and histone modifications for the modulation of HP1 chromatin binding ability and heterochromatin formation. By generating a human GFP:HP1α cell line, I aimed to identify new regulators of heterochromatin formation, and I have analysed for the first time on a living organism one of the known HP1-chromatin binding regulators, Repo-man/PP1. As histone variants have a crucial role on chromatin organization, I have also analysed and differentiated the role of two H2A.Z variants, H2A.Z.1 and H2A.Z.2, on chromatin organization, cell cycle and gene expression