OCT4 and SOX2 Work as Transcriptional Activators in Reprogramming Human Fibroblasts.

SOX2 and OCT4, in conjunction with KLF4 and cMYC, are sufficient to reprogram human fibroblasts to induced pluripotent stem cells (iPSCs), but it is unclear if they function as transcriptional activators or as repressors. We now show that, like OCT4, SOX2 functions as a transcriptional activator. We substituted SOX2-VP16 (a strong activator) for wild-type (WT) SOX2, and we saw an increase in the efficiency and rate of reprogramming, whereas the SOX2-HP1 fusion (a strong repressor) eliminated reprogramming. We report that, at an early stage of reprogramming, virtually all DNA-bound OCT4, SOX2, and SOX2-VP16 were embedded in putative enhancers, about half of which were created de novo. Those associated with SOX2-VP16 were, on average, stronger than those bearing WT SOX2. Many newly created putative enhancers were transient, and many transcription factor locations on DNA changed as reprogramming progressed. These results are consistent with the idea that, during reprogramming, there is an intermediate state that is distinct from both parental cells and iPSCs.

Narayan S ，Bryant G ，Shah S ，Berrozpe G ，Ptashne M ... -  《Cell Reports》

Enhanced human somatic cell reprogramming efficiency by fusion of the MYC transactivation domain and OCT4.

The development of human induced pluripotent stem cells (iPSCs) holds great promise for regenerative medicine. However the iPSC induction efficiency is still very low and with lengthy reprogramming process. We utilized the highly potent transactivation domain (TAD) of MYC protein to engineer the human OCT4 fusion proteins. Applying the MYC-TAD-OCT4 fusion proteins in mouse iPSC generation leads to shorter reprogramming dynamics, with earlier activation of pluripotent markers in reprogrammed cells than wild type OCT4 (wt-OCT4). Dramatic enhancement of iPSC colony induction efficiency and shortened reprogramming dynamics were observed when these MYC-TAD-OCT4 fusion proteins were used to reprogram primary human cells. The OCT4 fusion proteins induced human iPSCs are pluripotent. We further show that the MYC Box I (MBI) is dispensable while both MBII and the linking region between MBI/II are essential for the enhanced reprogramming activity of MYC-TAD-OCT4 fusion protein. Consistent with an enhanced transcription activity, the engineered OCT4 significantly stimulated the expression of genes specifically targeted by OCT4-alone, OCT4/SOX2, and OCT4/SOX2/KLF4 during human iPSC induction, compared with the wt-OCT4. The MYC-TAD-OCT4 fusion proteins we generated will be valuable tools for studying the reprogramming mechanisms and for efficient iPSC generation for humans as well as for other species.

Wang L ，Huang D ，Huang C ，Yin Y ，Vali K ，Zhang M ，Tang Y ... -  《-》

High-efficiency generation of induced pluripotent mesenchymal stem cells from human dermal fibroblasts using recombinant proteins.

Chen F ，Zhang G ，Yu L ，Feng Y ，Li X ，Zhang Z ，Wang Y ，Sun D ，Pradhan S ... -  《Stem Cell Research & Therapy》

Human fibroblast reprogramming to pluripotent stem cells regulated by the miR19a/b-PTEN axis.

He X ，Cao Y ，Wang L ，Han Y ，Zhong X ，Zhou G ，Cai Y ，Zhang H ，Gao P ... -  《PLoS One》

Critical POU domain residues confer Oct4 uniqueness in somatic cell reprogramming.

Jin W ，Wang L ，Zhu F ，Tan W ，Lin W ，Chen D ，Sun Q ，Xia Z ... -  《Scientific Reports》