The transcription activation domains of Fos and Jun induce DNA bending through electrostatic interactions

Transcription factor-induced DNA bending is essential for the assembly of active transcription complexes at many promoters. However, most eukaryotic transcription regulatory proteins have modular DNA-binding and activation domains, which appeared to exclude DNA bending as a mechanism of transcription activation by these proteins. We show that the transcription activation domains of Fos and Jun induce DNA bending. In chimeric proteins, the transcription activation domains induce DNA bending independent of the DNA-binding domains. DNA bending by the chimeric proteins is directed diametrically away from the transcription activation domains. Therefore, the opposite directions of DNA bending by Fos and Jun are caused, in part, by the opposite locations of the transcription activation domains relative to the DNA-binding domains in these proteins. DNA bending is reduced in the presence of multivalent cations, indicating that electrostatic interactions contribute to DNA bending by Fos and Jun. Consequently, regions outside the minimal DNA-binding domain can influence DNA structure, and may thereby contribute to the architectural reorganization of the promoter region required for gene activation.