Role of C-Domain of a NAC Transcription Factor for pH-Tuned DNA Binding of Its N-Domain with Histidine Switch

Affinity of transcription factors(TFs) to their target DNA is a critical determinant in gene expression. TFs are composed of DNA binding domain (DBD) and regulatory domains, intrinsically disordered and/or negatively charged. Asking whether DBD alone can regulate the transcriptional control is an important question for identifying the design principle of TFs. We studied ANAC019 TF, a member of 108 Arabidopsis plant TF family proteins, and found a well-conserved histidine-switch located in its DBD. It regulates both homo-dimerization and transcriptional control of ANAC019 TF through histidine-protonation. Here, we uncovered that the removal of C-terminal domain in ANAC019 TF abolishes pH dependent binding affinity of N-terminal DBD alone to target DNA. We suggested an underlying mechanism that ANAC019 DBD alone is too strongly attracted and has too long residency time near DNA to have pH dependent binding affinity. But its full-chain, possessing an electric dipole moment, could balance DBD's strong attraction to DNA.