KLF4 is a member of the Kruppel-like factor (KLF) family of zinc finger transcription factors. Members of this family have in common 3 contiguous C2H2-type zinc fingers at the carboxyl terminus that comprise the DNA-binding domain. KLF4 is highly expressed in skin and gut epithelial tissues, but is also found in various other cells and tissues, including vascular endothelial cells, lymphocytes, lung, and testis. It is an important regulator of the cell cycle, transcription, and cell differentiation. Together with Sox2, Oct4, and cMyc, KLF4 can induce the reprogramming of primary human fibroblasts to a pluripotent state. KLF4 and other transcription factors can be introduced into cells by DNA transfection, viral infection, or microinjection. Protein transduction using TAT fusion proteins represents an alternative methodology for introducing transcription factors into primary as well as transformed cells. Recombinant human KLF4-TAT is a 51.7 kDa protein containing 483 amino acid residues, including 13- residue C-terminal TAT peptide.