The function of histone H3 lysine 76 methylation in host-induced differentiation in Trypanosoma brucei
Final Report Abstract
Epigenetic mechanisms are important to change chromatin structure in order to regulate basic biological processes like transcription, DNA repair and cell cycle control. We use Trypanosoma brucei as a model system to study replication regulation and developmental differentiation and how they are controlled by chromatin-based mechanisms. Trypanosoma brucei is a unicellular parasite that causes sleeping sickness in humans and the “nagana” disease in livestock in African. Trypanosomes have a complex life cycle that includes two very different host environments: the vascular system and tissue fluids in the mammalian host and the intestinal tract and salivary glands of the vector, the tsetse fly. Trypanosomes developed a complicated life cycle in order to shuttle between different hosts. Many cellular functions of the parasite like energy metabolism, surface architecture, motility and cell cycle control require adaptation and specialization during differentiation. How trypanosomes regulate these processes is not well understood. In our work program, we want to investigate the contribution of chromatin reorganization during developmental differentiation that allows these parasites to adapt to different host environments. In an initial experiment, we compared the proteomes of two life cycle stages, bloodstream forms and insect forms, to learn more about the machinery that enables the parasite to adapt to different hosts. We then used this approach to monitor changes of protein expression during developmental differentiation by compared the proteomes at several time points during the differentiation process. Using our data in combination with information from the trypanosome database (TriTrypDB), we found several developmentally regulated chromatin-associated proteins that might be involved in the differentiation process. This now provides the basis for a series of follow-up experiments to unravel the function of these proteins in host adaptation. In the course of this project, we began to focus on the function of the histone methyltransferase DOT1B because DOT1B-depleted trypanosomes are not able to differentiate to the insect form of the parasite. After a detailed analysis of this phenotype, we concluded that loss of DOT1B- mediated histone methylation is responsible for defects in karyokinesis and possibly chromosome segregation during early developmental differentiation in trypanosomes. In addition to the detailed descriptive analysis of this DOT1B-mediated phenotype, we also established all cell biological and biochemical tools and collaborations needed to unravel the mechanistic events behind this phenotype in a continuing funding period.
Publications
- (2012) DOT1A-dependent H3K76 methylation is required for replication regulation in Trypanosoma brucei Nucleic Acids Res. Nov 1;40(20):10302-10311
A. Gassen, D. Brechtefeld, N. Schandry, J.M. Arteaga-Salas, L. Israel, A. Imhof, C.J. Janzen
(See online at https://doi.org/10.1093/nar/gks801) - (2013) Comparative proteomics of two life cycle stages of stable isotope-labeled Trypanosoma brucei reveals novel components of the parasite's host adaptation machinery Mol. Cell. Proteomics. Jan;12(1): 172-179
F. Butter, F. Bucerius, M. Michel, Z. Cicova, M. Mann, C.J. Janzen
(See online at https://doi.org/10.1074/mcp.M112.019224)
