SINUDYN

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.