Cooperative DNA binding and sequence discrimination by the Opaque2 bZIP factor.
The maize Opaque2 (O2) protein is a basic leucine zipper transcription factor that controls the expression of distinct classes of endosperm genes through the recognition of different cis-acting elements in their promoters. The O2 target region in the promoter of the alpha-coixin gene was analyzed in detail and shown to comprise two closely adjacent binding sites, named O2u and O2d, which are related in sequence to the GCN4 binding site. Quantitative DNase footprint analysis indicated that O2 binding to alpha-coixin target sites is best described by a cooperative model. Transient expression assays showed that the two adjacent sites act synergistically. This synergy is mediated in part by cooperative DNA binding. In tobacco protoplasts, O2 binding at the O2u site is more important for enhancer activity than is binding at the O2d site, suggesting that the architecture of the O2-DNA complex is important for interaction with the transcriptional machinery.
Yunes
J A
JA
Centro de Biologia Molecular e Engenharia Genética, Universidade Estadual de Campinas, 13083-970, Campinas, SP, Brazil.
Vettore
A L
AL
da Silva
M J
MJ
Leite
A
A
Arruda
P
P
D001483:Base Sequence; D050976:Basic-Leucine Zipper Transcription Factors; D001665:Binding Sites / Q000235:genetics; D002874:Chromosome Mapping; D015342:DNA Probes / Q000235:genetics; D018744:DNA, Plant / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D019143:Evolution, Molecular; D051790:G-Box Binding Factors; D015870:Gene Expression; D017343:Genes, Plant; D016350:Leucine Zippers / Q000235:genetics; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D003313:Zea mays / Q000235:genetics / Q000378:metabolism*
D050976:Basic-Leucine Zipper Transcription Factors; D015342:DNA Probes; D018744:DNA, Plant; D004268:DNA-Binding Proteins; D051790:G-Box Binding Factors; D010940:Plant Proteins; D014157:Transcription Factors; C067402:opaque-2 protein, Zea mays; C072398:alpha-coixin protein, Coix lacryma-jobi