Identification of three residues in the basic regions of the bZIP proteins GCN4, C/EBP and TAF-1 that are involved in specific DNA binding.

Abstract

The bZIP regions of the eukaryotic transcription factors GCN4 and C/EBP have similar protein sequences but they recognize different DNA sequences. In order to understand their specificity, a vector was constructed which permits overexpression in Escherichia coli of those domains of GCN4 that are necessary and sufficient for specific DNA binding i.e. the basic region and the leucine zipper. Specific DNA binding was monitored with gel shift experiments. The residues of the basic region of GCN4 were systematically replaced by those of C/EBP to transform GCN4 into C/EBP with respect to DNA binding. Residues −17, −16 and −14 were found to be responsible for switching GCN4 to C/EBP binding specificity (we define as residue +1 the first leucine of the first leucine heptad repeat of GCN4). We broadened the specificity of GCN4 to TAF‐1 by replacing residues −15 and −17 and we changed the specificity of C/EBP to TAF‐1 by swapping residue −17 of a particular hybrid. Thus residues positioned from −14 to −17 of the basic region play a key role in recognizing specific DNA sequences.

Stress-Induced Binding of the Transcription Factor CHOP to a Novel DNA Control Element

“…Alignment of the basic region of CHOP with that of other bZIP proteins reveals that residues found to impart sequencespecific DNA recognition in the case of other bZIP proteins are the ones predicted to break the basic-region helical structure in CHOP (19,41; also, see Fig. 2 in reference 35).…”

Directed mutation of the basic domain of v-Jun alters DNA binding specificity and abolishes its oncogenic activity in chicken embryo fibroblasts

“…Some members of this class of proteins exhibit similar binding speci®cities whereas others are completely di erent. For instance the yeast transcription factor GCN4 recognizes the same target sequence as c-Jun (TGACTCA) whereas c/ EBP binds a target much removed from this sequence (ATTGCGCAAT) (Johnson, 1993;Suckow et al, 1993). Mutational studies have demonstrated that the basic region adjacent to the leucine dimerization domain is directly responsible for speci®city of target recognition in this class of proteins.…”

“…Mutational studies have demonstrated that the basic region adjacent to the leucine dimerization domain is directly responsible for speci®city of target recognition in this class of proteins. Substitution of a few critical amino acids in the basic region of GCN4 with those found in c/EBP results in a mutant GCN4 protein in which DNA binding speci®city has been altered from TGACTCA (GCN4 target) to ATTGCG-CAAT (c/EBP target) (Johnson, 1993;Suckow et al, 1993). Mutants such as this have the advantage that they exhibit altered functional speci®city while retaining their structural integrity.…”

STF1 is a novel TGACG‐binding factor with a zinc‐finger motif and a bZIP domain which heterodimerizes with GBF proteins

“…The leucine residues within the leucine zipper are indicated as asterisks. The positions of the amino acids are numbered by taking the first leucine of the heptad repeat as position 1 (nomenclature according to Suckow et al, 1993). both STF proteins and the cellulose synthases can be interpreted as a two finger sequence: CCCC-CCCC.…”