title: The two homeodomains of the ZmHox2a gene from maize originated as an internal gene duplication and have evolved different target site specificities.
abstract: The maize ZmHox2a gene encodes two homeodomains which originated by a 699 bp duplication within an ancestral precursor. The sequences of the two ZmHox2a homeodomains are highly diverged in the N-terminal arm, while residues in the helical part have mostly been conserved. We show here that both ZmHox2a homeodomains are functional DNA-binding motifs but exhibit different target site specificities. CASTing experiments reveal a TCCT motif recognized by HD1 but a GATC tetranucleotide as the recognition sequence of HD2. Mutation of the central nucleotides in both tetranucleotide core motifs abolishes DNA binding. A domain swap experiment indicates that target site specificity is achieved in a combinatorial manner by the contributions of the diverged N-terminal arms together with the slightly different recognition helices. Computer modelling suggests that K47 and H54 in the recognition helices preferentially contact the bases at the 3'-terminus of the tetranucleotide target sequences.
authors.affiliation: Institut für Entwicklungsbiologie and Institut für Genetik, Universität zu Köln, Gyrhofstrasse 17, 50923 Köln, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Kirch
authors.forename: S
authors.initials: S
authors.lastname: Bitter
authors.forename: B
authors.initials: B
authors.lastname: Kisters-Woike
authors.forename: W
authors.initials: W
authors.lastname: Werr
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D001665:Binding Sites; D001667:Binding, Competitive; D003198:Computer Simulation; D016384:Consensus Sequence; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D019143:Evolution, Molecular; D020440:Gene Duplication; D005801:Genes, Homeobox; D017343:Genes, Plant; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides / Q000096:biosynthesis / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000302:isolation & purification; D013379:Substrate Specificity; D003313:Zea mays / Q000235:genetics* / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; C098999:Hox2a protein, Zea mays; D009838:Oligodeoxyribonucleotides; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins