Analysis of DNA binding specificities of plant class I TCP proteins.

RODRIGO RIPOLL; IVANA VIOLA; DANIEL GONZALEZ

Mendoza

Congreso; XLVIII Reunión Anual de la SAIB; 2012

SAIB

TCP genes encode plant-specific transcription factors with a noncanonical bHLH domain (the TCP domain) that allows DNA binding and protein–protein interactions. Based on sequence homology, TCP proteins can be divided in two classes, I and II. SELEX experiments using rice proteins suggested that proteins from each class have distinct DNA binding specificities (GTGGGNCC versus GTGGNCCC). To gain insight into the DNA binding properties of class I TCP transcription factors, we performed SELEX experiments with different Arabidopsis class I proteins. We have observed that TCP6, TCP11, TCP15, TCP16 and TCP20 have different DNA binding preferences. In the case of TCP11, this is correlated with the presence of Thr at position 15 of the TCP domain, while Asp11 is responsible for the different DNA binding properties of TCP16. In addition, heterodimers between TCP11 and TCP15 have different binding properties than the corresponding homodimers. Interestingly, the analysis of site-specific mutants and chimeras between TCP6 and TCP20 indicated that regions located outside the basic region are responsible for their different DNA binding properties. Altogether, our results suggest that class I TCP proteins display more variability in DNA binding preferences than previously thought.