KLF4 (Krueppel-like factor 4) is a transcription factor, can act both as activator and as repressor. KLF4 binds the 5'-CACCC-3' core sequence of promoters, and also binds to its own promoter region of its own gene and can activate its own transcription. KLF4 regulates the e, Xenopus/Amphibian,pression of key transcription factors during embryonic development. KLF4 plays an important role in maintaining embryonic stem cells, in preventing their differentiation. POU5F1/OCT4, SO, Xenopus/Amphibian,2,Mouse,YC/c-Myc and KLF4 are the four Yamanaka factors. When combined, these factors are sufficient to reprogram differenciated cells to an embryonic-like state designated iPS (induced pluripotent stem) cells. iPS cells e, Xenopus/Amphibian,hibit the morphology and growth properties of ES cells and e, Xenopus/Amphibian,press ES cell marker genes.