Periodic Reporting for period 1 - AMBITION (Unravelling the molecular Basis of epigenetic silencing: what factors define a gene as a Polycomb target?)
Reporting period: 2017-04-01 to 2019-03-31
An ideal system to study Polycomb targeting is a locus where epigenetic silencing can be induced externally, and the maintenance of silencing can be easily recorded during subsequent development. In the model plant Arabidopsis thaliana, the integration of complex developmental and environmental signals determining flowering time occurs via tight regulation of the floral repressor gene FLOWERING LOCUS C (FLC). At FLC, specific DNA binding proteins (VAL1, VAL2) and their partners interact in a not yet fully understood regulatory network with Polycomb proteins, which consequently converts environmental cues (prolonged cold) into stable epigenetic memory (silencing of the gene).
Building on previously identified proteomic interactions, the AMBITION project hypothesised that FLC regulation involves components of the Apoptosis and Splicing Associated Protein (ASAP) complex. ASAP functions in RNA processing and quality control, thus putatively linking VAL1 DNA sequence specificity with co-transcriptional regulation directly to Polycomb mediated epigenetic silencing. The project combined several interconnected molecular, biochemical and genetic avenues to provide novel and detailed mechanistic insights into the epigenetic regulation of Polycomb target genes.
In addition, the AMBITION project addressed the role of the Apoptosis and Splicing Associated Protein (ASAP) complex on FLC regulation during vernalization. Transgenic mutant lines have been created and analysed before, during and after cold treatment to attribute the effect of individual ASAP components on the transcriptional output and epigenetic state of FLC. Interestingly, single mutants show only subtle effects during vernalisation, but seem to regulate FLC transcript levels in the warm, similar to known co-transcriptional regulators of the autonomous pathway. Genetic studies have been conducted to understand potential cooperativity and functional interaction of ASAP proteins and in repressing FLC transcription and epigenetic silencing of the locus.
The results from the AMBITION project have not been yet been fully disseminated to the public. A manuscript is in preparation and will result in a timely open access publication in a peer-reviewed scientific journal according to the H2020 guidelines.