Fig. 6. Establishment of pluripotency in somatic cell nuclei. In a recent study (Takahashi and Yamanaka, 2006), four transcription factors, Oct3/4, Sox2, Klf4 and c-Myc, were found to be sufficient to establish pluripotency in the nuclei of fibroblasts. Oct3/4, Sox2 and Klf4 might function together to activate target genes to establish the stable pluripotent transcription factor network, as well as the pluripotent epigenome, whereas c-Myc might enhance the accessibility of target genes by stimulating DNA replication.