Changing POU dimerization preferences converts Oct6 into a pluripotency inducer.

Stepan Jerabek,Sergiy Velychko,Calista Kl Ng,Vlad Cojocaru,Marcos J Arauzo‐Bravo,Hans R Schöler,Caitlin M Maccarthy,Xiaoxiao Yang,Vikas Malik,Kee‐Pyo Kim,Guangming Wu,Daniel Esch,Ralf Jauch,Yanpu Chen

doi:10.15252/embr.201642958

Abstract

The transcription factor Oct4 is a core component of molecular cocktails inducing pluripotent stem cells (iPSCs), while other members of the POU family cannot replace Oct4 with comparable efficiency. Rather, group III POU factors such as Oct6 induce neural lineages. Here, we sought to identify molecular features determining the differential DNA‐binding and reprogramming activity of Oct4 and Oct6. In enhancers of pluripotency genes, Oct4 cooperates with Sox2 on heterodimeric SoxOct elements. By re‐analyzing ChIP‐Seq data and performing dimerization assays, we found that Oct6 homodimerizes on palindromic OctOct more cooperatively and more stably than Oct4. Using structural and biochemical analyses, we identified a single amino acid directing binding to the respective DNA elements. A change in this amino acid decreases the ability of Oct4 to generate iPSCs, while the reverse mutation in Oct6 does not augment its reprogramming activity. Yet, with two additional amino acid exchanges, Oct6 acquires the ability to generate iPSCs and maintain pluripotency. Together, we demonstrate that cell type‐specific POU factor function is determined by select residues that affect DNA‐dependent dimerization.

Highlights

The transcription factor Oct4 is a core component of molecular cocktails inducing pluripotent stem cells, while other members of the POU family cannot replace Oct4 with comparable efficiency
Consistent with de novo motif discovery, these analyses show that the more palindromic Oct factor recognition element” (MORE) motif predominates in somatic Oct binding sites, whereas the SoxOct motif is strongly enriched in the Oct4 binding sites of pluripotent cells (Fig EV1A)
Oct4 is a master regulator of pluripotency, and it is the only factor that cannot be substituted by any paralogous family member during inducing pluripotent stem cells (iPSCs) generation [2]

Summary

Introduction

The transcription factor Oct is a core component of molecular cocktails inducing pluripotent stem cells (iPSCs), while other members of the POU family cannot replace Oct with comparable efficiency. We sought to identify molecular features determining the differential DNA-binding and reprogramming activity of Oct and Oct. In enhancers of pluripotency genes, Oct cooperates with Sox on heterodimeric SoxOct elements. Using structural and biochemical analyses, we identified a single amino acid directing binding to the respective DNA elements. A change in this amino acid decreases the ability of Oct to generate iPSCs, while the reverse mutation in Oct does not augment its reprogramming activity. With two additional amino acid exchanges, Oct acquires the ability to generate iPSCs and maintain pluripotency. We demonstrate that cell type-specific POU factor function is determined by select residues that affect DNA-dependent dimerization

Methods

Results

Conclusion