Isolation of two soybean G-box binding factors which interact with a G-box sequence of an auxin-responsive gene.
G-box binding factors (GBFs) constitute a family of plant DNA-binding proteins that bind to the G-box motif, a regulatory cis element present in many plant genes with a palindromic DNA motif of CACGTG. Previously TCCACGTGTC, a G-box motif, from an auxin responsive gene GmAux28 has been identified as a sequence-specific protein-binding site. Here the isolation of two soybean cDNA clones, referred to as SGBF-1 and SGBF-2, encoding proteins which bind to the G-box motif is reported. The primary structure of SGBF-1 and SGBF-2 predicts that these proteins contain a basic leucine zipper (bZIP) DNA-binding domain and an N-terminal proline-rich domain. A dramatic difference in the pattern of protein-DNA complex formation was observed when recombinant SGBF-1 and SGBF-2 proteins were analyzed by electrophoretic mobility shift assays (EMSAs). The SGBF-1 binding pattern obtained with the G-box probe resulted in three major retarded bands while the SGBF-2 formed a single complex. This shows that the characteristically diffuse banding pattern of plant nuclear proteins interacting with the G-box is also observed in a binding assay using only one recombinant GBF. EMSAs were performed with a few selected binding sequences to study the effect of flanking nucleotides to the hexanucleotide G-box core motif. The binding specificity of the SGBF proteins resembles that described for type A cauliflower nuclear G-box binding proteins which bind class I G-box elements [(G/T)(C/A)CACGTG(G/T)(A/C)]. Phylogenetic analysis of 13 GBF-like proteins from various plant species reveals that the SGBF-1 and SGBF-2 proteins belong to different lineages, suggesting that they may have distinct functions in activating transcription.
Hong
J C
JC
Plant Molecular Biology and Biotechnology Research Center, Gyeongsang National University, Chinju, Korea.
Cheong
Y H
YH
Nagao
R T
RT
Bahk
J D
JD
Key
J L
JL
Cho
M J
MJ
D000595:Amino Acid Sequence; D001483:Base Sequence; D050976:Basic-Leucine Zipper Transcription Factors; D015152:Blotting, Northern; D015139:Blotting, Southern; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D018744:DNA, Plant / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D051790:G-Box Binding Factors; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant / Q000235:genetics; D007210:Indoleacetic Acids / Q000378:metabolism*; D008969:Molecular Sequence Data; D005810:Multigene Family / Q000235:genetics; D011485:Protein Binding; D011487:Protein Conformation; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics*; D017422:Sequence Analysis, DNA; D013025:Glycine max / Q000235:genetics*; D014157:Transcription Factors
D050976:Basic-Leucine Zipper Transcription Factors; D018076:DNA, Complementary; D018744:DNA, Plant; D004268:DNA-Binding Proteins; D051790:G-Box Binding Factors; D007210:Indoleacetic Acids; D014157:Transcription Factors