Structural Insights of Induced Pluripotent Stem Cell Regulatory Factors Oct4 and Its Interaction with Sox2 and Fgf4 Gene

Abstract

Pluripotency of stem cells is governed by various factors, and Octamer-binding transcription factor 4 (Oct4) has been shown to be most essential regulator of Embryonic Stem Cells (ESCs) pluripotency. It is a key molecule for the reprogramming process and vastly used for IPSCs generation in research laboratories. Oct4 interacts directly with another important molecule Sox2 and elicitvarious downstream signals during the reprogramming. Sox2 is sex determining region-Y protein and involved in reprogramming through interaction with Oct4 and other pluripotency factors. Both of these transcription factors are known to bind enhancer element of specific genes regulating pluripotency such as fibroblast growth factor 4 (Fgf4) gene. Fgf4 has been proposed to promote self-renewation in human ESCs and support proliferation of mouse inner cell mass. The molecular mechanism for Oct4 interactions with Sox2 and their target gene(s) remain cryptic. The present study focuses on these aspects, and a comprehensive in silico analysis of Oct4-Sox2 and Fgf4 structure and their interactions are reported here. Briefly, the Three-Dimensional (3D) models of Oct4 and Sox2 were generated and analyzed using de novo structure prediction approach. Further, these molecules were used to define the mechanism of their interactions to each other (Oct4 and Sox2); and their complex interaction with Fgf4 gene by molecular docking. The interaction of proteins and enhancer element of Fgf4 gene and resulting complexes were further evaluated through Dim plot analysis. This work reports that Oct4 binds to Sox2 with significant stability as indicated by their binding energy score (-618.95 kJ/mol) and two hydrogen bonds in between Gly307-Ser228 of 2.97 A and Glu219-His260 of 3.02 A bond lengths with hydrophobic interfaces. More importantly, we found that Oct4 in complex formation with Sox2 bind moreefficientlywithscore-615.86kJ/molthenOct4andSox2bindsindividuallywiththescoreof-585.22 and -395.99 kJ/mol respectively. We suggest Oct4-Sox2 complex play a crucial role by synergistically increasing their binding to enhancer element of Fgf4 gene. Insights into the molecular mechanism of interaction of Oct4 and Sox2 would help to better understand the reprogramming regulatory network.