Chromatin Dynamics In Homology Directed Repair

This thesis consist of six chapters and the appendices. Each chapter starts with a brief summary page. If parts or the whole of the chapter has been published, that sheet indicates the title, author list and the date of the publication as well as my personal contribution to the papers. Chapter I is an overview of chromatin organization and dynamics in the context of DNA double-strand break (DSB) repair. Chapter II is a specific published guideline for DNA recombination and repair studies. This chapter is an extracted section of my contribution to a published review. It describes the method I used to visualize and quantify chromosomal dynamics upon DNA double strand breaks in yeast S. cerevisiae. Chapter III describes my main thesis research question, results, discussion and experimental procedures. This study show that DNA damage induced histone depletion enhances homology search through the induced chromatin expansion and ectopic locus mobility, independently of local DSB movement. Moreover, we show that local DSB dynamics is cell cycle dependent and is regulated by Cohesin turnover. Finally, we find that centromeres do not detach upon DNA damage. Chapter IV in an overview of the roles of two post-translational modifications (PTMs) in the regulation of DNA repair pathway choice in budding yeast: Ubiquitination and the small ubiquitin-related modifier protein (SUMO). This chapter introduces the research context to Chapter V. Chapter V contains a study to which I had contributed in which we reported that the presence of telomeric repeat sequences on one side of a double-strand break alters the outcome of repair. We show that the two sides of the break show uncoordinated movement and are repaired asymmetrically leading to translocation. We observed that the repair outcome is tightly controlled by SUMO targeted ubiquitin ligases. Chapter VI summarizes the main conclusion of this thesis and discusses the results stemming from Chapter III together with relevant future directions. Finally, the appendices contain a list of abbreviations, my curriculum vitae and acknowledgments