Biological significance of the histone variant H3.3 (completed)
Our genome is organized into chromatin domains with different biochemical properties influencing gene expression. These domains can be distinguished by their enrichment in combinations of modified histones and in histone variants.
Foci of histone variant H3.3 with associated chaperones in stem cell nuclei.
While the significance of histone modifications has been studied since the discovery of the “histone code”, little is known for histone variants.
About the project
The goal of this 3-year project is to characterize the molecular mechanism of incorporation of histone H3.3 into chromatin and unravel its function in stem cell differentiation. The project contains two main objectives, namely: 1) provide genome-wide coverage of H3.3 enrichment sites in stem and differentiated cells; 2) Unveil the mechanistic details of H3.3 incorporation into chromatin.
The experimental strategy combines state-of-the-art genome-scale epigenomics and bioinformatics, quantitative imaging, biochemical fractionation, and stem cell biology, along with high-throughput sequencing and mass spectrometry technologies.
The project contains two main objectives, namely: 1) provide genome-wide coverage of H3.3 enrichment sites in stem and differentiated cells; 2) unveil the mechanistic details of H3.3 incorporation into chromatin.
Preliminary data to this project show an unsuspected and novel multi-step targeting of newly synthesized epitope-tagged H3.3 to chromatin via PML bodies. H3.3 is recruited to PML bodies in a DAXX--dependent manner, a process facilitated by ASF1A. Chaperones co-localize with H3.3 at PML bodies and are found in one or more complexes with PML.
Our data support a model of DAXX-mediated recruitment of (H3.3-H4) dimers to PML bodies, which may function as “triage centers” for H3.3 deposition into chromatin by distinct chaperones. We are currently testing the “triage center” hypothesis.
The project is co-financed by The Research Council of Norway and the University of Oslo.
- Dr. Lee Wong, Monash University, Melbourne, Australia
- Slimane Ait-Si-Ali, CNRS, Université Paris XI, Paris, France
Start - finish
01.09.12 – 31.08.15