Transcription factor; can act both as activator and as repressor. Binds the 5'-CACCC-3' core sequence (PubMed:10431239, PubMed:10556311, PubMed:15358627, PubMed:16954384, PubMed:17060454, PubMed:19816951, PubMed:20071344, PubMed:29593216). Binds to the promoter region of its own gene and can activate its own transcription (PubMed:10431239, PubMed:10556311, PubMed:15358627, PubMed:16954384, PubMed:17060454, PubMed:19816951, PubMed:20071344, PubMed:29593216). Regulates the expression of key transcription factors during embryonic development (PubMed:10431239, PubMed:10556311, PubMed:15358627, PubMed:16954384, PubMed:17060454, PubMed:19816951, PubMed:20071344, PubMed:29593216). Plays an important role in maintaining embryonic stem cells, and in preventing their differentiation (PubMed:10431239, PubMed:10556311, PubMed:15358627, PubMed:16954384, PubMed:17060454, PubMed:19816951, PubMed:20071344, PubMed:29593216). Required for establishing the barrier function of the skin and for postnatal maturation and maintenance of the ocular surface. Involved in the differentiation of epithelial cells and may also function in skeletal and kidney development. Contributes to the down-regulation of p53/TP53 transcription (By similarity). Interacts with MUC1 (via the C-terminal domain) (By similarity). Interacts with POU5F1/OCT4 and SOX2 (PubMed:19816951). Interacts with MEIS2 isoform MeisD and PBX1 isoform PBX1a (By similarity). Interacts with ZNF296 (PubMed:24161396). Interacts with GLIS1 (By similarity). Interacts with BTRC; this interaction leads to KLF4 ubiquitination and subsequent degradation (PubMed:29593216). Highest expression in the colon. Lower levels in testis, lung and small intestine. By interferon-gamma in Stat1-dependent manner. the 9aaTAD motif is a transactivation domain present in a large number of yeast and animal transcription factors. Ubiquitinated. 'Lys-48'-linked ubiquitinated and targeted for proteasomal degradation by the SCF(BTRC) E3 ubiquitin-protein ligase complex, thereby negatively regulating cell pluripotency maintenance and embryogenesis. Polyglutamylated by TTLL1 and TTLL4 at Glu-381, which inhibits KLF4 binding with E3 ligase component BTRC, thereby impeding ubiquitination (PubMed:29593216). Deglutamylated by CCP1 and CCP6; deglutamylation promotes KLF4 ubiquitination (PubMed:29593216). KLF4 glutamylation state plays a critical role in the regulation of its function in cell reprogramming, pluripotency maintenance and embryogenesis (PubMed:29593216). Death shortly after birth due to loss of epidermal barrier function resulting from perturbation of late-stage epidermal differentiation structures including the cornified envelope. When selectively deleted in the surface ectoderm-derived structures of the eye, embryos develop normally and adults are viable and fertile but mutants display down-regulation of Krt12 and Aqp5 and multiple ocular defects including corneal epithelial fragility, stromal edema, defective lens and loss of conjunctival goblet cells. POU5F1/OCT4, SOX2, MYC/c-Myc and KLF4 are the four Yamanaka factors. When combined, these factors are sufficient to reprogram differentiated cells to an embryonic-like state designated iPS (induced pluripotent stem) cells. iPS cells exhibit the morphology and growth properties of ES cells and express ES cell marker genes. Belongs to the krueppel C2H2-type zinc-finger protein family. Truncated N-terminus. Truncated N-terminus.