Molecular analysis of the mechanisms linking co-transcriptional RNA processing with chromatin silencing

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We have been studying the molecular pathways controlling flowering time in plants and this has led us into the study of a particular pathway, the autonomous pathway, which accelerates flowering by repressing a specific gene encoding a floral repressor. This pathway turns out to regulate many targets in the nucleus and not just genes regulating flowering time. A component of the autonomous pathway is a protein that binds RNA called FCA. FCA regulates the gene encoding a floral repressor, not through post-transcriptional mechanisms as suggested by its RNA-binding properties, but through a process where the transcription of the target is affected. FCA requires the activity of a second protein (FLD) that modifies the proteins (histones) intimately packaged with the DNA. We will undertake experiments to unravel how the sequence of events in gene silencing involving these proteins. This system is an excellent one to dissect a general and important question in molecular biology - how non-coding RNA drives chromatin changes. We will address how a particular RNA is selected for FCA binding and how this triggers the chromatin modification activity and thus the silencing of the locus. We will analyse one transcript in detail and then explore the generality of our findings. This work has the potential to reveal fundamental concepts important to gene regulation in many organisms.