Determinants of the DNA binding specificity of class I and class II TCP transcription factors.

IVANA VIOLA; RENATA REINHEIMER; RODRIGO RIPOLL; NORA UBERTI MANASSERO; DANIEL GONZALEZ

JOURNAL OF BIOLOGICAL CHEMISTRY

AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC

Año: 2012 vol. 287 p. 347 - 356

0021-9258

TCP proteins constitute a family of plant transcription factors with more than 20 members in angiosperms. They can be divided in two classes based on sequence homology and the presence of an insertion within the basic region of the TCP DNA binding and dimerization domain. Here, we describe binding site selection studies with the class I protein TCP16, showing that its DNA binding preferences are similar to those of class II proteins. Through sequence comparison and the analysis of mutants and chimeras of TCP16, TCP20 (class I) and TCP4 (class II), we established that the identity of residue 11 of the class I TCP domain or the equivalent residue 15 of the class II domain, whether it is Gly or Asp, determines a preference for a class I or a class II sequence, respectively. Footprinting analysis indicated that specific DNA contacts related with these preferences are established with one of the strands of DNA. The dimerization motif also influences the selectivity of the proteins towards class I and class II sequences and determines a requirement of an extended basic region in proteins with Asp15. We postulate that diferences in orientation of base-contacting residues brought about by the presence of either Gly or Asp are responsible for the binding site preferences of TCP proteins. Expression of repressor forms of TCP16 with Asp11 or Gly11 differently affects leaf development. TCP16-like proteins with Asp11 in the TCP domain arose in rosids and may be related with developmental characteristics of this lineage of eudicots.