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N-terminal domain of Kruppel-like factor 4 Kruppel-like factor 4 (KLF4; also known as Krueppel-like factor 4 or gut-enriched Kruppel-like factor/GKLF) is a protein that, in humans, is encoded by the KLF4 gene. Evidence also suggests that KLF4 is a tumor suppressor in certain cancers, including colorectal cancer, gastric cancer, esophageal squamous cell carcinoma, intestinal cancer, prostate cancer, bladder cancer and lung cancer. It may act as a tumor promoter where increased KLF4 expression has been reported, such as in oral squamous cell carcinoma and in primary breast ductal carcinoma. KLF4 is one of four key factors that are essential for inducing pluripotent stem cells. KLF4 is highly expressed in non-dividing cells and its overexpression induces cell cycle arrest. KLF proteins KLF1, KLF2, KLF4, KLF5, KLF6, and KLF7 are transcriptional activators. KLF4 belongs to a family of proteins called the Specificity Protein (SP)/KLF family, characterized by a C-terminal DNA-binding domain of 81 amino acids consisting of three Kruppel-like C2H2 zinc fingers. These factors bind to a loose consensus motif, namely NNRCRCCYY (where N is any nucleotide; R is A/G, and Y is C/T), such as the recurring motifs in GC and GT boxes (5'-GGGGCGGGG-3' and 5-GGTGTGGGG-3') that are present in promoters and more distal regulatory elements of mammalian genes. Members of the KLF family can act as activators or repressors of transcription depending on cell and promoter context. KLFs regulate various cellular functions, such as proliferation, differentiation, and apoptosis, as well as the development and homeostasis of several types of tissue. In addition to the C-terminal DNA-binding domain, each KLF also has a unique N-terminal activation/repression domain that confers specificity and allows it to bind specifically to a certain partner, leading to distinct activities in vivo. This model represents the N-terminal domain of KLF4, which is related to the N-terminal domains of KLF1 and KLF2. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",