Abstract 5767: DNA Binding Mechanism of Prostate Cancer Target ONECUT2

Abstract Transcription factors (TF) are essential determinants of gene regulation and their aberrant expression frequently drive cancers. The binding of TFs to cognate DNA is central to their role in gene regulation. An understanding of their DNA binding mechanism is, therefore, of fundamental and therapeutic relevance. Generally, TFs bind DNA through defined DNA binding domains. The CUT and homeodomain are two such evolutionarily conserved elements found paired in multiple transcription factor families including ONECUT (OC), POU, CUX and SATB. However, the mechanism of cross-talk between the CUT and homeodomain to coordinatedly bind DNA remains unknown. Here, we report an integrative DNA binding analyses of the transcription factor OC2, a promising target for treatment of aggressive prostate cancer. We demonstrate that the homeodomain of OC2 thermodynamically stabilizes the DNA binding through allosteric modulation of CUT. The binding energetics is further dependent on base interactions by evolutionarily conserved amino acids in both CUT and homeodomain. In addition, we have discovered a unique arginine pair in the homeodomain, conserved within the ONECUT family, but not across POU and SATB families. We show that one arginine of this pair binds distinctly to DNA in respective complexes formed by OC2 and OC1. Notably, the above base-interactions are crucial for OC2-driven disease progression in a prostate cancer cell-line model. Taken together, our studies show that base-interactions by the evolutionarily conserved residues determine the basic DNA binding functionality through establishing favorable thermodynamics, while interactions by the arginine motif impart family-specific attributes. These findings also establish the homeodomain as a key regulator of DNA binding by OC2 and provide a mechanism for cooperative DNA binding by the CUT-homeodomain module in general. Importantly, these insights reveal vulnerabilities for therapeutic targeting of OC2. Citation Format: Avradip Chatterjee, Brad Gallent, Madhusudhanarao Katiki, Chen Qian, Matthew R. Harter, Michael R. Freeman, Ramachandran Murali. DNA binding mechanism of prostate cancer target ONECUT2 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5767.