Structural mechanism of DNA-mediated Nanog-Sox2 cooperative interaction.

The efficiency of stem cell transcriptional regulation always depends on the cooperative association and expression of transcription factors (TFs). Among these, Oct4, Sox2, and Nanog play major roles. Their cooperativity is facilitated direct protein-protein interactions or DNA-mediated interactions, yet the mechanism is not clear. Most biochemical studies have examined Oct4/Sox2 cooperativity, whereas few studies have evaluated how Nanog competes in the connection between these TFs. In this study, using computational models and molecular dynamics simulations, we built a framework representing the DNA-mediated cooperative interaction between Nanog and Sox2 and analyzed the plausible interaction factors experienced by Nanog because of Sox2, its cooperative binding partner. Comparison of a wild-type and mutant Nanog/Sox2 model with the Nanog crystal structure revealed the regulatory structural mechanism between Nanog/Sox2-DNA-mediated cooperative bindings. Along with the transactivation domains interaction, the DNA-mediated allosteric interactions are also necessary for Nanog cooperative binding. DNA-mediated Nanog-Sox2 cooperativity influences the protein conformational changes and a stronger interaction profile was observed for Nanog-Mut (L103E) in comparison with the Nanog-WT complex.