Characterization of the regulatory complexes around TELOMERE REPEAT BINDING FACTORS that determine epigenetic repression
 

The project will be supervised by Franziska Turck at the Max Planck Institute for Plant Breeding Research.

Abstract:

Epigenetic mechanisms control the expression of key developmental genes in multicellular organisms. One important epigenetic pathway relies on Polycomb Repressive Complexes (PRCs), which repress target genes by chromatin compaction. PRCs do not contain sequence-specific DNA-binding protein domains and therefore rely on interactions with transcription factors to find target regions. A regulatory network of cis-motifs, transcription factors, and PRC subunits determines which gene cohorts remain repressed or active during different phases of development. Our group focuses on PRC2 recruitment by TELOMERE REPEAT BINDING FACTORS (TRBs), which repress flower organ identity genes in leaf tissue prior to flowering. TRBs bind telobox-motifs on the DNA and physically interact with PRC2 components. Although TRB binding may lead to epigenetic repression of targets, we are still unable to predict the epigenetic outcome since TRBs can also promote the opposite outcome, high expression of target genes. Our work hypothesis is that co-factors and partner motifs determine the effect of TRB binding. The aim of this project is to characterize the function of TRB co-factors that were previously identified by mass spectroscopy. To achieve this goal, multi-gene mutants will be generated in Arabidopsis thaliana by genome editing. The generated material will be characterized by comparing phenotypes, transcriptomes and epigenetic changes. In addition, the binding patterns of TRBs and TRB-interacting transcription factors will be compared by genome-wide approaches (ChIPmentation). To round up the analysis, the effects of cis-motif combinations on epigenetic repression will be confirmed by a transgenic approach.

Key Publication: Zhou, Y. et al. Telobox motifs recruit CLF/SWN-PRC2 for H3K27me3 deposition via TRB factors in Arabidopsis. Nat Genet 50, 638-644 (2018)

Link to the Turck group homepage: https://www.mpipz.mpg.de/turck

 

Role of TRB INTERACTING TRANSCRIPTION FACTORS (TIFs) in gene regulation. A) NAC50/52 are TIFs and also bind JMJ14, a histone de-methylase, which removes the PcG antagonistic mark H3K4me3. B) BPCs do not directly interact with TRBs but their cognate motif (GAGA-motif) is reported to co-operates with the telobox in gene repression. Some BPCs were shown to interact with PRC2 core components and the PRC2-associated protein LHP1. C) TCPs do not directly interact with TRBs but their cognate motif (site II motif) is required for gene activation in combination with telobox motifs. Possibly, TCP recruit PcG-antagonistic complexes. D) Several TIFs were identified. Their role in epigenetic gene repression (or an antagonistic role) is not yet known.
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