TGA1 and G-box binding factors: two distinct classes of Arabidopsis leucine zipper proteins compete for the G-box-like element TGACGTGG.
Regulatory elements containing the sequence ACGT are found in several plant promoters and are recognized by various basic/leucine zipper (bZIP) proteins. The Arabidopsis G-box binding factor 1 (GBF1), initially identified by its ability to bind to the palindromic G-box (CCACGTGG), also interacts with the TGACGT motif if this hexamer sequence is followed by either the dinucleotide GG--as found in the Hex motif of the wheat histone 3 promoter--or GT. Here we describe the isolation of an Arabidopsis bZIP protein, denoted TGA1, that also recognizes ACGT-containing sequences. However, TGA1 differs from members of the GBF family in the spectrum of base pair permutations flanking the ACGT sequence that are required for DNA binding. TGA1 primarily requires a TGACG motif and preferentially binds to those pentamers that are followed by a T residue. We show that although both TGA1 and GBF1 bind to the Hex motif (TGACGTGG), this binding can be distinguished on the basis of their specific DNA-protein contacts. Furthermore, TGA1 also differs from members of the GBF family in that it apparently does not form heterodimers with any member of this family.
Schindler
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Department of Biology, University of Pennsylvania, Philadelphia 19104-6018.
Beckmann
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Cashmore
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AR
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000737:chemistry / Q000235:genetics*; D001483:Base Sequence; D050976:Basic-Leucine Zipper Transcription Factors / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification; D001667:Binding, Competitive; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification; D005786:Gene Expression Regulation; D017343:Genes, Plant; D016350:Leucine Zippers / Q000502:physiology*; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D010940:Plant Proteins / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification; D012045:Regulatory Sequences, Nucleic Acid; D014157:Transcription Factors / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification
D050976:Basic-Leucine Zipper Transcription Factors; D004268:DNA-Binding Proteins; D010940:Plant Proteins; C000588817:TGA1 protein, Arabidopsis; C065794:TGA1a protein, Nicotiana tabacum; D014157:Transcription Factors