Exposure to extended heat-stress induces large-scale nucleosome dynamics and leads to reactivation of transcriptional silencing illustrating a yet undefined layer of epigenetic control, as epigenetic marks commonly associated with reactivation of transcriptional silencing are unaffected.
Our aim is to gain insight into the mechanisms controlling nucleosome dynamics and transcriptional changes induced by exposure to prolonged heat stress. Based on the observation that lack of some histone chaperone subunits caused slower re-silencing and incomplete restoration of nucleosomes, we systematically investigate the role of histone H3 variants and all H3/H4 histone chaperones as possible elements in the control of histone eviction and nucleosome re-assembly during heat stress.
We develop plants with altered histone dynamics or expressing tagged histones. This material is analyzed with complementing assays, including quantitative imaging analysis of chromatin compaction, RNA sequencing and chromatin immunoprecipitation followed by deep sequencing. Together, this will allow studying nucleosomal occupancy, transcription, extent and specificity of differential histone eviction, reassembly and post-translational modifications of nucleosomes induced by heat stress.
This project strengthens the intensive collaboration between the two partner teams and will pave the way for fruitful interactions in the future. Indeed, we have already obtained a PHC (Partenariat Hubert Curien) fellowship that finances travel expenses between the two partner laboratories.
Our unique material and tools together with the development of new technological advances allows us to gain insight into the mechanisms controlling nucleosome dynamics during heat stress. In addition, information and tools are valuable assets to further explore the general mechanism of histone turnover outside S-phase and the challenge it presents to epigenetic maintenance.
A ce jour, aucune publication n’est encore issue de ce projet collaboratif.
Chromosomal DNA in eukaryotes is organized into chromatin with nucleosomes as basic subunits. The histones in the nucleosomal core are highly conserved proteins, with several variants that can carry specific post-translational modifications. Nucleosome position and composition are important elements of epigenetic information that, together with the genomic DNA, can be inherited during somatic and sexual propagation. DNA sequence information is copied faithfully during replication and hence represents the most conservative layer of inheritance. In contrast, arrangement, composition, and modification of the nucleosomes can vary during growth, or between tissues and individual cells, thereby affecting gene expression patterns and contributing substantially to differentiation and development. Besides these programmed changes at nucleosomes, recent data from one partner lab have shown that in plants, also extended exposure to high temperature can cause extensive and global dissociation of nucleosomes from DNA, connected with transcriptional activation of otherwise silent genes and transposons. Although these gene expression changes are transient, they result in a lasting effect on the organization of heterochromatin in nuclei of differentiated leaf cells. Reassembly of nucleosomes requires the chromatin assembly factor (CAF) complex, a well-conserved histone H3-H4 chaperone. In the context of the proposed project, we want to build on this work and investigate the molecular processes occurring during nucleosome dis- and re-association and the nature of the persistent effects on nuclear chromatin organization. To this end, we will focus in particular on the role of histone H3-H4 chaperones in the removal of old and supply of new histones as well as on the dynamics and chromatin enrichment of different H3 variants. Further, we want to investigate the extent to which the heat stress-induced changes also affect meristematic tissue. This is an important question as environmentally induced epigenetic changes are presumed to affect subsequent generations, but evidence on the molecular level is lacking. We will combine one team’s expertise in the molecular biology of histone variants, histone chaperones, and cytological analysis of nuclear organization with the know-how of the partner lab in stress application, analysis of global transcription, and nucleosome occupancy. The project is expected to provide insight into the mechanism of an interesting and so far under-investigated layer of epigenetic control and into the potential impact of adverse environmental conditions on inheritance. The project leaders have an established record of fruitful collaboration and will involve several young scientists in this work, for whom the research is an excellent training platform in a scientifically stimulating and well-equipped academic surrounding.
Madame Aline Probst (Genetique, Reproduction et Developpement) – firstname.lastname@example.org
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
GMI Gregor Mendel Institut of Molecular Plant Biology
GReD - CNRS Genetique, Reproduction et Developpement
Help of the ANR 210,704 euros
Beginning and duration of the scientific project: August 2013 - 36 Months