title: Identification of specific DNA binding residues in the TCP family of transcription factors in Arabidopsis.
abstract: The TCP transcription factors control multiple developmental traits in diverse plant species. Members of this family share an approximately 60-residue-long TCP domain that binds to DNA. The TCP domain is predicted to form a basic helix-loop-helix (bHLH) structure but shares little sequence similarity with canonical bHLH domain. This classifies the TCP domain as a novel class of DNA binding domain specific to the plant kingdom. Little is known about how the TCP domain interacts with its target DNA. We report biochemical characterization and DNA binding properties of a TCP member in Arabidopsis thaliana, TCP4. We have shown that the 58-residue domain of TCP4 is essential and sufficient for binding to DNA and possesses DNA binding parameters comparable to canonical bHLH proteins. Using a yeast-based random mutagenesis screen and site-directed mutants, we identified the residues important for DNA binding and dimer formation. Mutants defective in binding and dimerization failed to rescue the phenotype of an Arabidopsis line lacking the endogenous TCP4 activity. By combining structure prediction, functional characterization of the mutants, and molecular modeling, we suggest a possible DNA binding mechanism for this class of transcription factors.
authors.affiliation: Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore 560 012, India.
authors.forename: Pooja
authors.initials: P
authors.lastname: Aggarwal
authors.forename: Mainak
authors.initials: M
authors.lastname: Das Gupta
authors.forename: Agnel Praveen
authors.initials: AP
authors.lastname: Joseph
authors.forename: Nirmalya
authors.initials: N
authors.lastname: Chatterjee
authors.forename: N
authors.initials: N
authors.lastname: Srinivasan
authors.forename: Utpal
authors.initials: U
authors.lastname: Nath
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000235:genetics; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics; D018257:Helix-Loop-Helix Motifs / Q000235:genetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016296:Mutagenesis; D054730:Protein Interaction Domains and Motifs; D016415:Sequence Alignment; D014157:Transcription Factors / Q000737:chemistry* / Q000235:genetics
chemical_list: D029681:Arabidopsis Proteins; D004268:DNA-Binding Proteins; D014157:Transcription Factors