title: Identification of the residues in the Myb domain of maize C1 that specify the interaction with the bHLH cofactor R.
abstract: The maize Myb transcription factor C1 depends on the basic helix-loop-helix (bHLH) proteins R or B for regulatory function, but the closely related Myb protein P does not. We have used the similarity between the Myb domains of C1 and P to identify residues that specify the interaction between the Myb domain of C1 and the N-terminal region of R. Substitution of four predicted solvent-exposed residues in the first helix of the second Myb repeat of P with corresponding residues from C1 is sufficient to confer on P the ability to physically interact with R. However, two additional Myb domain amino acid changes are needed to make the P regulatory activity partially dependent on R in maize cells. Interestingly, when P is altered so that it interacts with R, it can activate the Bz1 promoter, normally regulated by C1 + R but not by P. Together, these findings demonstrate that the change of a few amino acids within highly similar Myb domains can mediate differential interactions with a transcriptional coregulator that plays a central role in the regulatory specificity of C1, and that Myb domains play important roles in combinatorial transcriptional regulation.
authors.affiliation: Department of Plant Biology and Plant Biotechnology Center, Ohio State University, Columbus, OH 43210, USA. 1Wosu.edu
authors.forename: E
authors.initials: E
authors.lastname: Grotewold
authors.forename: M B
authors.initials: MB
authors.lastname: Sainz
authors.forename: L
authors.initials: L
authors.lastname: Tagliani
authors.forename: J M
authors.initials: JM
authors.lastname: Hernandez
authors.forename: B
authors.initials: B
authors.lastname: Bowen
authors.forename: V L
authors.initials: VL
authors.lastname: Chandler
mesh_terms: D000595:Amino Acid Sequence; D051792:Basic Helix-Loop-Helix Proteins; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D020598:Proto-Oncogene Proteins c-myb / Q000737:chemistry / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism*; D020798:Two-Hybrid System Techniques; D003313:Zea mays / Q000378:metabolism*
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D004268:DNA-Binding Proteins; D020598:Proto-Oncogene Proteins c-myb; D014157:Transcription Factors