GABPα Binding to Overlapping ETS and CRE DNA Motifs Is Enhanced by CREB1: Custom DNA Microarrays.

To achieve proper spatiotemporal control of gene expression, transcription factors cooperatively assemble onto specific DNA sequences. The ETS domain protein monomer of GABP alpha and the B-ZIP domain protein dimer of CREB1 cooperatively bind DNA only when the ETS (C/G CGGAAGT) and CRE (GTGACGTCAC) motifs overlap precisely, producing the ETS <-> CRE motif (C/G CGGAAGTGACGTCAC). We designed a Protein Binding Microarray (PBM) with 60-bp DNAs containing four identical sectors, each with 177,440 features that explore the cooperative interactions between GABP alpha and CREB1 upon binding the ETS <-> CRE motif. The DNA sequences include all 15-mers of the form C/G CGGA--CG-, the ETS <-> CRE motif, and all single nucleotide polymorphisms (SNPs), and occurrences in the human and mouse genomes. CREB1 enhanced GABP alpha binding to the canonical ETS <-> CRE motif CCGGAAGT two-fold, and up to 23-fold for several SNPs at the beginning and end of the ETS motif, which is suggestive of two separate and distinct allosteric mechanisms of cooperative binding. We show that the ETS-CRE array data can be used to identify regions likely cooperatively bound by GABP alpha and CREB1 in vivo, and demonstrate their ability to identify human genetic variants that might inhibit cooperative binding.