KLF3, originally termed Basic Krüppel-like Factor (BKLF), was the third member of theKrüppel-like factor family ofzinc fingertranscription factors to be discovered.[5] Transcription factors in this family bind DNA by virtue of 3 characteristic three C2H2zinc fingers at theirC-termini. Since their DNA-binding domains are highly conserved within the family, all KLF proteins recognize CACCC or CGCCC boxes of the general form NCR CRC CCN, (where N is any base and R is apurine).
While the C-termini are similar in different KLFs, theN-termini vary and accordingly different KLFs can either activate or repress transcription or both. KLF3 appears to function predominantly as arepressor of transcription. It turns genes off. It does this by recruiting the C-terminal Binding Protein co-repressorsCTBP1 andCTBP2.[6][7] CtBP docks onto a short motif (residues 61-65) in the N-terminus of KLF3, of the general form Proline – Isoleucine – Aspartate – Leucine – Serine (the PIDLS motif).[6][7] CtBP in turn recruitshistone modifying enzymes to alterchromatin and repress gene expression.
KLF3 is expressed highly in the red blood cell or erythroid lineage. Here it is driven by another KLF, Erythroid KLF orKLF1, and its expression increases as erythroid cells mature. Studies inknockout mice reveal a mild anemia in the absence of functional KLF3 and the de-repression of several target genes that contain CACCC boxes in their regulatory regions.[8] Many of these genes are activated by KLF1, hence it appears that KLF3 operates in anegative feedback loop to balance the activating potential of KLF1. KLF3 also regulates another repressive KLF,KLF8.[9] Thus KLF1, KLF3 and KLF8 operate in a tight regulatory network. KLF3 and KLF8 may have redundant functions, as mice lacking both KLF3 and KLF8 show defects that are more severe than in either single knockout. They die in utero around day 14 of gestation.[10]
As well as being expressed in erythroid cells, KLF3 is present in other cell types and analysis of theknockout mice has revealed defects affectingadipose tissue[11] andB cells.[12] KLF3 deficient mice have less adipose tissue and indications of metabolic health that may be attributable to de-repression of theadipokine hormone geneadipolin.[13] The role of KLF3 in B lymphocytes is complex but it appears to operate in a network with KLF2 andKLF4 to influence the switch betweenspleenmarginal zone andfollicular B cells.[14]
Turner J, Crossley M (2000). "Basic Krüppel-like factor functions within a network of interacting haematopoietic transcription factors".Int. J. Biochem. Cell Biol.31 (10):1169–74.doi:10.1016/S1357-2725(99)00067-9.PMID10582345.
Wang MJ, Qu XH, Wang LS, Zhai Y, Wu SL, He FC (2003). "cDNA cloning, subcellular localization and tissue expression of a new human Krüppel-like transcription factor: human basic Krüppel-like factor (hBKLF)".Yi Chuan Xue Bao.30 (1):1–9.PMID12812068.
