Functional Characterization of Arabidopsis thaliana DCX E3 ligase activities

• Applicant: Professor Dr. Thomas Schmülling, since 3/2007
• Subject Area: Plant Genetics and Genomics
• Term: from 2006 to 2009
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 31785174

Cullins are central scaffolding subunits in eukaryotic E3 ligases that facilitate ubiquitination of target proteins within the ubiquitin proteasome pathway. In preliminary works we have demonstrated complex assembly of a potential Arabidopsis thaliana DCX E3 ligase that consists of the CULLIN 4 (AtCUL4), the DNA-Damaged Binding 1a (AtDDB1a) protein and the RING-finger protein AtRBX1. In addition we could also demonstrate interaction of AtDDB1a with AtDDB2,1, a potential substrate protein. In animals and human, the DCX-complex and DDB2 play critical roles in development and UV-dependent DNA repair. Although very little is known about the function and biological roles of these proteins preliminary analysis in plants of AtCUL4 mutants show that the cullin is highly important for whole plant development. The goal of this project is to explain DCX-E3 ligase function in Arabidopsis, and this shall be achieved by accomplishing five crucial work points: 1) Establishing interacting partner proteins of AtCUL4, AtDDB1a, and AtDDB2,1, 2) Detailed expression analysis of DCX-subunits and selected substrates, 3) Studying sub cellular protein localization and their dynamics, 4) Demonstrating E3 ubiquitin ligase activity and regulatory mechanisms triggering these E3 ligase activities, and 5) Characterization of single and multiple mutant phenotypes with a focus on development and changed stress response.

• DFG Programme: Research Grants
• Ehemaliger Antragsteller: Professor Dr. Hanjo Hellmann, until 3/2007