Protein-protein and protein-DNA interaction studies of A. thaliana class I TCP transcription factors

IVANA L. VIOLA; DANIEL H. GONZALEZ

Carlos Paz. Córdoba. Argentina

Congreso; XLIV REUNIÓN ANUAL de la SOCIEDAD ARGENTINA DE INVESTIGACIÓN EN BIOQUÍMICA Y BIOLOGÍA MOLECULAR; 2008

SAIB

TCP proteins are plant-specific transcription factors involved in the regulation of cell growth and proliferation. These proteins contain the TCP domain, a basic helix-loop-helix (bHLH) structure required for DNA binding and dimerization, unrelated to the canonical bHLH found in eukaryotic proteins. Members of the TCP family can be grouped into two classes, I and II. The DNA sequences recognized by both classes share a core sequence but differ in flanking nucleotides. To characterize the DNA binding properties of class I proteins, we performed in vitro DNA binding assays with oligonucleotides containing variants of the previously determined consensus binding site and proteins TCP11, TCP20, TCP15 and TCP21 from A. thaliana. The results showed that, while subtle differences in nucleotide preferences were evident for the other proteins, TCP11 shows a clearly different DNA binding specificity. A more detailed picture of binding to DNA was obtained by missing nucleoside experiments with hydroxyl radical. These assays indicated the presence of different contacts in the interaction of TCP proteins with DNA. We also identified potential TCP11 interaction partners by yeast two-hybrid screening. In vitro and in vivo protein-protein interaction assays revealed that TCP11 interacts with TCP15 and TCP21. Finally, the DNA binding and dimerization specificity of class I TCP proteins is discussed.