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RNA-Binding Proteins and Post-Transcriptional Control in the Circadian System
Circadian rhythms
Organisms have evolved endogenous circadian clocks with a period of about 24 h that allow synchronization with the periodic changes in light and temperature in the outside world. Plants with a functional circadian clock have an enhanced performance and fitness because they correctly phase their daily life to the light/dark cycle in the environment.
Underlying these endogenous circadian rhythms like photosynthetic activity, growth or hormonal levels, is a transcriptional network under control of the circadian clock: Almost 90% of transcripts in Arabidopsis accumulate at defined times of the day.
The circadian transcriptome
The core clockwork comprises transcriptional feedback loops with positively and negatively acting proteins that regulate expression of their own genes and thus generate a self-sustained 24 h oscillation.
Our research focuses on RNA-binding proteins and posttranscriptional regulation in the circadian system.
The RNA-binding protein AtGRP7
The RNA-binding protein At GRP7 ( Arabidopsis thaliana glycine-rich RNA-binding protein 7) is part of a molecular slave oscillator downstream of the Arabidopsis core clockwork. At GRP7 negatively autoregulates oscillations of its own mRNA by alternative splicing coupled to Nonsense-mediated decay. At GRP8 encoding a related RRM-protein is not only an At GRP7 target but in turn also negatively autoregulates and reciprocally cross-regulates At GRP7. Thus, we identify an interlocked feedback loop through which two RNA-binding proteins autoregulate and reciprocally crossregulate by coupling unproductive splicing to NMD. It appears that the two RNA-binding proteins fine-tune their expression through this cross-regulation and effectively buffer against disturbances.
Transcript profiling of transgenic plants ectopically overexpressing At GRP7 compared to wt plants has identified candidate At GRP7 target transcripts.
In collaboration with the Department of Laser Physics we have used Fluorescence Correlation Spectroscopy to study the interaction of At GRP7 with its RNA target and conformational dynamics of the RNA substrate. Photoelectron transfer (PET) based fluorescence was used to assay conformational dynamics of the RNA binding substrates.
In collaboration with the Department of Biophysics and Nanotechnology we have adapted Atomic Force Microscopy to study RNA-protein interaction at the single molecule level.