Étude des mécanismes de régulation de l'activité du complexe acétyltransférase NuA4
|Abstract:||Chromatin, which basic unit is the nucleosome, is a very dynamic structure that requires remodeling during nuclear processes that need to access the DNA such as replication, transcription and DNA damage repair. A number of remodeling factors have been characterized and include histone chaperone, ATP-dependent remodelers, histone variants and post-translational histone modifiers. The NuA4 acetyltransferase complex, responsible for H4 and H2A acetylation, participates in chromatin and nucleosome dynamics associated to these nuclear processes. It was shown to promote chromatin relaxation during transcription activation and DNA repair. NuA4 is the only acetyltransferase complex essential for viability in the yeast Saccharomyces cerevisiae. The objective of my Ph.D. project was to understand the mechanisms that regulate NuA4’s activity. We brought to the forefront tree different ways to control NuA4’s activity, via its auto-acetylation, its specific targeting to the chromatin and via its histone substrate. While acetylation of the Yng2 subunit of NuA4 by NuA4 itself is important for maintenance of the integrity and activity of the complex, we discovered that NuA4 is capable of in vivo and in vitro auto-acetylation of several of its subunits. In addition, we showed that the acetylation of a single lysine residue located in the MYST domain of the catalytic subunit Esa1 is essential for the activity of the complex and has no effect on its integrity. On another hand, we have characterized a sub-complex of NuA4 composed by the Eaf5, Eaf7 and the chromodomain-containing Eaf3 proteins that are implicated in NuA4 targeting to the chromatin. This trimeric complex is also found in the cell independent of NuA4 and preferentially associated to gene coding region. Finally, published works from our laboratory showed that post-translational modifications of H4 N-ter tail can regulate NuA4 activity. Phosphorylation of H4 serine1 inhibits its acetylation on adjacent lysines by NuA4. We demonstrated that this mark is specifically induced on coding region of active genes and that this phosphorylation would be implicated in chromatin dynamics associated with the transcription elongation process.|
|Document Type:||Thèse de doctorat|
|Open Access Date:||18 April 2018|
|Collection:||Thèses et mémoires|
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