Isolation of a Gene Encoding a Functional Zinc Finger Protein Homologous to Erythroid Krüppel-Like Factor: Identification of a New Multigene Family

Abstract

We have identified and characterized the gene for a novel zinc finger transcription factor which we have termed lung Krüppel-like factor (LKLF). LKLF was isolated through the use of the zinc finger domain of erythroid Krüppel-like factor (ELKF) as a hybridization probe and is closely related to this erythroid cellspecific gene. LKLF is expressed in a limited number of tissues, with the predominant expression seen in the lungs and spleen. The gene is developmentally controlled, with expression noted in the 7-day embryo followed by a down-regulation at 11 days and subsequent reactivation. A high degree of similarity is noted in the zinc finger regions of LKLF and EKLF. Beyond this domain, the sequences diverge significantly, although the putative transactivation domains for both LKLF and EKLF are proline-rich regions. In the DNA-binding domain, the three zinc finger motifs are so closely conserved that the predicted DNA contact sites are identical, suggesting that both proteins may bind to the same core sequence. This was further suggested by transactivation assays in which mouse fibroblasts were transiently transfected with a human ␤-globin reporter gene in the absence and presence of an LKLF cDNA construct. Expression of the LKLF gene activates this human ␤-globin promoter containing the CACCC sequence previously shown to be a binding site for EKLF. Mutation of this potential binding site results in a significant reduction in the reporter gene expression. LKLF and EKLF can thus be grouped as members of a unique family of transcription factors which have discrete patterns of expression in different tissues and which appear to recognize the same DNA-binding site.

Krüppel-like Factors: Three Fingers in Many Pies

“…GenBank TM accession numbers for protein sequences used for this analysis are as follows: hKLF1, U37106; mKLF1, M97200; hKLF2, Q9Y5W3; hKLF3, P57682; hKLF4, O43474; hKLF5, XP_007199; hKLF6, AF001461; hKLF7, XP_002291; hKLF8, NP_009181; hKLF9, XP_005584; hKLF10, NP_005646; hKLF11, AAF75793; hKLF12, CAB46982; hKLF13, NP_057079; mKLF14, CAC06698; hKLF15, BAA88561. Developmental expression patterns of the murine homologues of many of these have also been determined: KLF1 (36), KLF2 (30,31) …”

The Krüppel-like Factor Epiprofin Is Expressed by Epithelium of Developing Teeth, Hair Follicles, and Limb Buds and Promotes Cell Proliferation

“…This protein family can be divided into several classes by its sequence and functional similarities, including an Sp1-like subgroup and two KLF subgroups. Some of these proteins, such as Sp1 and BTEB1/KLF9, are ubiquitously expressed (11,12), whereas others, such as EKLF/KLF1 and LKLF/KLF2, are expressed in a tissue-specific manner (13,14). KLF13 and KLF14/Sp6 were identified by screening a mouse expressed sequence tag data base using the Sp1 zinc finger domain as a probe and were reported to be ubiquitous by RT-PCR analysis (1).…”

Altered DNA-binding specificity mutants of EKLF and Sp1 show that EKLF is an activator of the β-globin locus control region in vivo

“…The G boxes are bound by members of a transcription factor family characterized by the presence of three zinc fingers highly homologous to those found in Sp1. The Sp1 family includes ubiquitously expressed proteins like Sp1 (Kadonaga et al 1987), Sp3 (Hagen et al 1992;Kingsley and Winoto 1992), basic transcription element binding protein (BTEBs; Imataka et al 1992) and basic Krü ppel-like factor (BKLF; Crossley et al 1996), and tissue-restricted factors like gut-enriched Krü ppel-like factor (GKLF; Shields et al 1996), lung Krü ppel-like factor (LKLF; Anderson et al 1995), and erythroid Krü ppel-like factor (EKLF; Miller and Bieker 1993). Moreover, a large number of Sp1-like zinc finger domains can be found in the expressed sequence tag (EST) databases.…”