RESUMO
DORNROSCHEN (DRN) (also known as ENHANCER OF SHOOT REGENERATION1; ESR1) and DRN-LIKE (DRNL; also known as ESR2) are two linked paralogues encoding AP2 domain-containing proteins. drn mutants show embryo cell patterning defects and, similarly to drnl mutants, disrupt cotyledon development at incomplete penetrance. drn drnl double mutants with weak or strong drnl alleles show more highly penetrant and extreme phenotypes, including a pin-like embryo without cotyledons, confirming a high degree of functional redundancy for the two genes in embryo patterning. Altered expression of PIN1::PIN1-GFP and DR5::GFP in drn mutant embryos places DRN upstream of auxin transport and response. A yeast two-hybrid screen with DRN followed by co-immunoprecipitation and bimolecular fluorescence complementation revealed PHAVOLUTA (PHV) to be a protein interaction partner in planta. drn phv double mutants show an increased penetrance of embryo cell division defects. DRNL can also interact with PHV and both DRN and DRNL can heterodimerise with additional members of the class III HD-ZIP family, PHABULOSA, REVOLUTA, CORONA and ATHB8. Interactions involve the PAS-like C-terminal regions of these proteins and the DRN/DRNL AP2 domain.
Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/embriologia , Regulação da Expressão Gênica de Plantas , Proteínas de Homeodomínio/metabolismo , Fatores de Transcrição/metabolismo , Sequência de Aminoácidos , Arabidopsis/genética , Arabidopsis/metabolismo , Proteínas de Arabidopsis/química , Proteínas de Arabidopsis/genética , Cotilédone/embriologia , Dimerização , Proteínas de Homeodomínio/química , Proteínas de Homeodomínio/genética , Ácidos Indolacéticos/metabolismo , Dados de Sequência Molecular , Mutação , Estrutura Terciária de Proteína , Sementes/metabolismo , Fatores de Transcrição/química , Fatores de Transcrição/genética , Técnicas do Sistema de Duplo-HíbridoRESUMO
Eukaryotic transcriptional regulation often involves regulatory elements separated from the cognate genes by long distances, whereas appropriately positioned insulator or enhancer-blocking elements shield promoters from illegitimate enhancer action. Four proteins have been identified in Drosophila mediating enhancer blocking-Su(Hw), Zw5, BEAF32 and GAGA factor. In vertebrates, the single protein CTCF, with 11 highly conserved zinc fingers, confers enhancer blocking in all known chromatin insulators. Here, we characterize an orthologous CTCF factor in Drosophila with a similar domain structure, binding site specificity and transcriptional repression activity as in vertebrates. In addition, we demonstrate that one of the insulators (Fab-8) in the Drosophila Abdominal-B locus mediates enhancer blocking by dCTCF. Therefore, the enhancer-blocking protein CTCF and, most probably, the mechanism of enhancer blocking mediated by this remarkably versatile factor are conserved from Drosophila to humans.
