Sox Transcription Factors Require Selective Interactions with Oct4 and Specific Transactivation Functions to Mediate Reprogramming

Authors

  • Irene Aksoy,

    1. Stem Cell and Developmental biology, Genome Institute of Singapore, Singapore
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  • Ralf Jauch,

    1. Laboratory for Structural Biochemistry, Genome Institute of Singapore, Singapore
    2. Guangzhou Institutes for Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, People's Republic of China
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  • Volker Eras,

    1. Stem Cell and Developmental biology, Genome Institute of Singapore, Singapore
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  • Wen-bin Alfred Chng,

    1. Stem Cell and Developmental biology, Genome Institute of Singapore, Singapore
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  • Jiaxuan Chen,

    1. Stem Cell and Developmental biology, Genome Institute of Singapore, Singapore
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  • Ushashree Divakar,

    1. Stem Cell and Developmental biology, Genome Institute of Singapore, Singapore
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  • Calista Keow Leng Ng,

    1. Laboratory for Structural Biochemistry, Genome Institute of Singapore, Singapore
    2. School of Biological Sciences, Nanyang Technological University, Singapore
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  • Prasanna R. Kolatkar,

    1. Laboratory for Structural Biochemistry, Genome Institute of Singapore, Singapore
    2. Department of Biological Sciences, National University of Singapore, Singapore
    3. Qatar Biomedical Research Institute, Doha, Qatar
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  • Lawrence W. Stanton

    Corresponding author
    1. Stem Cell and Developmental biology, Genome Institute of Singapore, Singapore
    2. School of Biological Sciences, Nanyang Technological University, Singapore
    3. Department of Biological Sciences, National University of Singapore, Singapore
    • Correspondence: Lawrence W. Stanton, Ph.D., Genome Institute of Singapore, 60 Biopolis Street #02-01, 138672, Singapore. Telephone: +65-68088006; Fax: +65-68088291; e-mail: stantonl@gis.a-star.edu.sg; or Prasanna R Kolatkar, Ph.D., Qatar Biomedical Research Institute, P.O. Box 5825, Doha, Qatar. Telephone: +974 4454 5889; Fax: +65–68088291; e-mail: pkolatkar@qf.org.qa

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  • Author contributions: I.A.: conception and design, collection and/or assembly of data, data analysis and interpretation, manuscript writing, and final approval of manuscript; R.J.: conception and design, manuscript writing, and final approval of manuscript; V.E., A.C.W.B., J.C., U.D., and C.K.L.N.: collection of data; P.K. and L.W.S.: financial support, administrative support, data analysis and interpretation, manuscript writing, final approval of manuscript. I.A. and R.J. contributed equally to this article.

Abstract

The unique ability of Sox2 to cooperate with Oct4 at selective binding sites in the genome is critical for reprogramming somatic cells into induced pluripotent stem cells (iPSCs). We have recently demonstrated that Sox17 can be converted into a reprogramming factor by alteration of a single amino acid (Sox17EK) within its DNA binding HMG domain. Here we expanded this study by introducing analogous mutations to 10 other Sox proteins and interrogated the role of N-and C-termini on the reprogramming efficiency. We found that point-mutated Sox7 and Sox17 can convert human and mouse fibroblasts into iPSCs, but Sox4, Sox5, Sox6, Sox8, Sox9, Sox11, Sox12, Sox13, and Sox18 cannot. Next we studied regions outside the HMG domain and found that the C-terminal transactivation domain of Sox17 and Sox7 enhances the potency of Sox2 in iPSC assays and confers weak reprogramming potential to the otherwise inactive Sox4EK and Sox18EK proteins. These results suggest that the glutamate (E) to lysine (K) mutation in the HMG domain is necessary but insufficient to swap the function of Sox factors. Moreover, the HMG domain alone fused to the VP16 transactivation domain is able to induce reprogramming, albeit at low efficiency. By molecular dissection of the C-terminus of Sox17, we found that the β-catenin interaction region contributes to the enhanced reprogramming efficiency of Sox17EK. To mechanistically understand the enhanced reprogramming potential of Sox17EK, we analyzed ChIP-sequencing and expression data and identified a subset of candidate genes specifically regulated by Sox17EK and not by Sox2. Stem Cells 2013;31:2632–2646

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