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Updated: May 15, 2026

Direct Induction of Hemogenic Endothelium and Blood by Overexpression of Transcription Factors in Human Pluripotent Stem Cells
Published on: December 3, 2015
Pluripotency transcription factor Sox2 is strongly adsorbed by heparin but requires a protein transduction domain for
Cem Albayrak1, William C Yang, James R Swartz
1Department of Chemical Engineering, Stanford University, 381 North-South Mall, Stanford, CA 94305, USA.
Abstract:
The binding of protein transduction domain (PTD)-conjugated proteins to heparan sulfate is an important step in cellular internalization of macromolecules. Here, we studied the pluripotency transcription factor Sox2, with or without the nonaarginine (R9) PTD. Unexpectedly, we observed that Sox2 is strongly adsorbed by heparin and by the fibroblasts without the R9 PTD. However, only the R9Sox2 fusion protein is internalized by the cells. These results collectively show that binding to heparan sulfate is not sufficient for cellular uptake, thereby supporting a recent hypothesis that other proteins play a role in cell internalization of PTD-conjugated proteins.
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