Biophysical characterization of the transcription factor SOG1 from Arabidopsis thaliana

Samenvatting

One of the world’s biggest agronomical problems concerns the reduced crop productivity in areas with acidic soils. Knowing that the global percentages of acidic soils and the world population will keep rising, and that soil acidification is an irreversible process, sustainable solutions are more than ever needed. The reduced crop yield is the consequence of a DNA damage-induced cell cycle arrest of the root cells at low pH. The plant-specific transcription factor SOG1 plays a major role in inducing this growth arrest by inhibiting the CDK-CYC complexes that are required for the transition to the next cell cycle phase. It has been found that plants with disabled SOG1 do not experience any inhibition of root growth.
SOG1 is a member of the NAC domain super family from which most proteins consist of an N-terminal NAC domain (responsible for both DNA binding and dimerization) and a C-terminal intrinsically disordered domain. For SOG1, this latter domain is suspected to modulate the activity of the NAC domain. SOG1 contains additionally an N-terminal extension for which the function is unclear. Although it has already been found that SOG1 forms dimers in solution, no further details about its three-dimensional structure, its mechanism of action or the way it is regulated are known.
This thesis aims to reveal the residues of SOG1 that are crucial for DNA binding and dimerization. Based on previous studies, six out of seven selected residues in SOG1 (lysine-63, glutamate-70, lysine-129, arginine-136, arginine-139, glycine-155) were investigated by mutating them individually within the context of both full-length SOG1 and its isolated SOG1NAC domain. The generated SOG1 mutants were expressed in insect cells while the expression of the SOG1NAC mutants was performed in an E. coli strain. The wild-type protein and selected mutants were purified and studied using EMSA and analytical gel filtrations. From these experiments, it can be concluded that lysine-63 is involved in dimerization and that arginine-139 and glycine-155 both contribute to the DNA binding mechanism. Further investigations are still required for complete understanding of the structure and the regulation mechanism of SOG1.

Datum prijs	2 jul. 2018
Originele taal	English
Prijsuitreikende instantie	Vrije Universiteit Brussel
Begeleider	Remy Loris (Promotor), Henri De Greve (Promotor), Manon Demulder (Advisor), Yann Sterckx (Jury) & Daniel Charlier (Jury)