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Isolation of two soybean G‐box binding factors which interact with a G‐box sequence of an auxin‐responsive gene
Author(s) -
Hong Jong Chan,
Cheong Yong Hwa,
Nagao Ron T.,
Bahk Jeong Dong,
Key Joe L.,
Cho Moo Je
Publication year - 1995
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1046/j.1365-313x.1995.08020199.x
Subject(s) - leucine zipper , sequence motif , biology , bzip domain , b3 domain , dna binding protein , cyclic nucleotide binding domain , caat box , binding site , gene , dna , binding protein , transcription factor , genetics , peptide sequence , gene expression , promoter
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.