In vitro, genomic context identification of transcription factor binding sites for bZIP C/S1 homodimers and heterodimers

In eukaryotes, many transcription factors (TF) usually form dimers or oligomers with itself or other TFs to regulate gene expression. To study how homo- and heterodimerization of TFs affect DNA binding specificity, we developed a double DNA Affinity Purification sequencing (double DAP-seq; dDAP-seq) technique that maps heterodimer binding sites in endogenous genome context and applied it to elucidate the binding profiles of homo- and heterodimers of the Group C and S1 basic leucine zipper (bZIP) transcription factors in Arabidopsis. Genome-wide binding profiles of twenty pairs of bZIP C/S1 heterodimers and bZIP S1 homodimers revealed that heterodimerization significantly expands the DNA binding preferences of homodimers, creating unique binding sites and target gene functions. In addition to the classical ACGT elements recognized by plant bZIPs, we found the Group C/S1 dimers bind to sequence motifs that might share an origin with the yeast bZIP GCN4. Further analysis of heterodimer-specific binding sequences uncovered two types of motif recognition patterns that mediate heterodimer specificity. Our study shed light on the functions and mechanisms of TF dimerization and demonstrated the potential of dDAP-seq in deciphering the complexity of these interactions within or across TF families. Identification of binding sites for homodimers and heterodimers of bZIP transcription factors in Arabidopsis by direct sequencing of affinity purified genomic DNA fragments. Please note that the processed data files generated from multiple/merged samples are indicated in the corresponding sample description field and are linked as Series supplemenatary files.