scholarly journals The Ikaros gene encodes a family of functionally diverse zinc finger DNA-binding proteins.

1994 ◽  
Vol 14 (12) ◽  
pp. 8292-8303 ◽  
Author(s):  
A Molnár ◽  
K Georgopoulos
Keyword(s):  
Dna Binding ◽  
Zinc Finger ◽  
Ectopic Expression ◽  
Regulatory Elements ◽  
Lymphocyte Development ◽  
Sequence Specificity ◽  
Alternate Splicing ◽  
Gene Encoding ◽  
Regulatory Pathways ◽  
Functionally Diverse

We previously described the lymphocyte-restricted Ikaros gene encoding a zinc finger DNA-binding protein as a potential regulator of lymphocyte commitment and differentiation. Here, we report the isolation of four additional Ikaros transcripts, products of alternate splicing that encode functionally diverse proteins. The Ikaros proteins contain unique combinations of zinc finger modules that dictate their overall sequence specificity and affinity. The Ik-1 and Ik-2 proteins can both bind, albeit with different affinities, to the same recognition sequences present in a number of lymphocyte-specific regulatory elements. The Ik-3 and the Ik-4 proteins interact only with a subset of these motifs. The Ik-1 and Ik-2 proteins can strongly stimulate transcription, whereas Ik-3 and Ik-4 are weak activators. Significantly, the transcription activation potential of the Ikaros proteins correlates with their subcellular localization. Upon ectopic expression of the Ikaros isoforms in nonlymphoid cells, Ik-1 and Ik-2 localize to the nucleus, whereas Ik-3 and Ik-4 are predominantly found in the cytoplasm. The Ikaros isoforms are expressed differentially in lymphocytes: Ik-1 and Ik-2 mRNAs are the predominating forms, and Ik-4 is present in significant amounts only in early T-cell progenitors, whereas Ik-3 and Ik-5 transcripts are expressed at relatively low levels throughout lymphocyte development. The ability of the Ikaros gene to generate functionally diverse proteins that may participate in distinct regulatory pathways substantiates its role as a master regulator during lymphocyte development.

The Ikaros gene encodes a family of functionally diverse zinc finger DNA-binding proteins

1994 ◽  
Vol 14 (12) ◽  
pp. 8292-8303
Author(s):  
A Molnár ◽  
K Georgopoulos
Keyword(s):  
Dna Binding ◽  
Zinc Finger ◽  
Ectopic Expression ◽  
Regulatory Elements ◽  
Lymphocyte Development ◽  
Sequence Specificity ◽  
Alternate Splicing ◽  
Gene Encoding ◽  
Regulatory Pathways ◽  
Functionally Diverse

We previously described the lymphocyte-restricted Ikaros gene encoding a zinc finger DNA-binding protein as a potential regulator of lymphocyte commitment and differentiation. Here, we report the isolation of four additional Ikaros transcripts, products of alternate splicing that encode functionally diverse proteins. The Ikaros proteins contain unique combinations of zinc finger modules that dictate their overall sequence specificity and affinity. The Ik-1 and Ik-2 proteins can both bind, albeit with different affinities, to the same recognition sequences present in a number of lymphocyte-specific regulatory elements. The Ik-3 and the Ik-4 proteins interact only with a subset of these motifs. The Ik-1 and Ik-2 proteins can strongly stimulate transcription, whereas Ik-3 and Ik-4 are weak activators. Significantly, the transcription activation potential of the Ikaros proteins correlates with their subcellular localization. Upon ectopic expression of the Ikaros isoforms in nonlymphoid cells, Ik-1 and Ik-2 localize to the nucleus, whereas Ik-3 and Ik-4 are predominantly found in the cytoplasm. The Ikaros isoforms are expressed differentially in lymphocytes: Ik-1 and Ik-2 mRNAs are the predominating forms, and Ik-4 is present in significant amounts only in early T-cell progenitors, whereas Ik-3 and Ik-5 transcripts are expressed at relatively low levels throughout lymphocyte development. The ability of the Ikaros gene to generate functionally diverse proteins that may participate in distinct regulatory pathways substantiates its role as a master regulator during lymphocyte development.

scholarly journals CbfA, the C-Module DNA-Binding Factor, Plays an Essential Role in the Initiation of Dictyostelium discoideum Development

2004 ◽  
Vol 3 (5) ◽  
pp. 1349-1358 ◽  
Author(s):  
Thomas Winckler ◽  
Negin Iranfar ◽  
Peter Beck ◽  
Ingo Jennes ◽  
Oliver Siol ◽  
...  
Keyword(s):  
Dna Binding ◽  
Cell Density ◽  
Dictyostelium Discoideum ◽  
Ectopic Expression ◽  
Development Program ◽  
Cell Physiology ◽  
Dependent Manner ◽  
Wild Type ◽  
Gene Encoding ◽  
Multicellular Development

ABSTRACT We recently isolated from Dictyostelium discoideum cells a DNA-binding protein, CbfA, that interacts in vitro with a regulatory element in retrotransposon TRE5-A. We have generated a mutant strain that expresses CbfA at <5% of the wild-type level to characterize the consequences for D. discoideum cell physiology. We found that the multicellular development program leading to fruiting body formation is highly compromised in the mutant. The cells cannot aggregate and stay as a monolayer almost indefinitely. The cells respond properly to prestarvation conditions by expressing discoidin in a cell density-dependent manner. A genomewide microarray-assisted expression analysis combined with Northern blot analyses revealed a failure of CbfA-depleted cells to induce the gene encoding aggregation-specific adenylyl cyclase ACA and other genes required for cyclic AMP (cAMP) signal relay, which is necessary for aggregation and subsequent multicellular development. However, the cbfA mutant aggregated efficiently when mixed with as few as 5% wild-type cells. Moreover, pulsing cbfA mutant cells developing in suspension with nanomolar levels of cAMP resulted in induction of acaA and other early developmental genes. Although the response was less efficient and slower than in wild-type cells, it showed that cells depleted of CbfA are able to initiate development if given exogenous cAMP signals. Ectopic expression of the gene encoding the catalytic subunit of protein kinase A restored multicellular development of the mutant. We conclude that sensing of cell density and starvation are independent of CbfA, whereas CbfA is essential for the pattern of gene expression which establishes the genetic network leading to aggregation and multicellular development of D. discoideum.

scholarly journals Isolation of a gene encoding a functional zinc finger protein homologous to erythroid Krüppel-like factor: identification of a new multigene family.

1995 ◽  
Vol 15 (11) ◽  
pp. 5957-5965 ◽  
Author(s):  
K P Anderson ◽  
C B Kern ◽  
S C Crable ◽  
J B Lingrel
Keyword(s):  
Dna Binding ◽  
Binding Site ◽  
Zinc Finger ◽  
Reporter Gene ◽  
Zinc Finger Protein ◽  
Erythroid Cell ◽  
Specific Gene ◽  
Beta Globin ◽  
Gene Encoding ◽  
Hybridization Probe

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 cell-specific 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 beta-globin reporter gene in the absence and presence of an LKLF cDNA construct. Expression of the LKLF gene activates this human beta-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.

Importance of a flanking AT-rich region in target site recognition by the GC box-binding zinc finger protein MIG1

1994 ◽  
Vol 14 (3) ◽  
pp. 1979-1985
Author(s):  
M Lundin ◽  
J O Nehlin ◽  
H Ronne
Keyword(s):  
Dna Binding ◽  
Zinc Finger ◽  
Zinc Finger Protein ◽  
Wilms Tumor ◽  
Glucose Repression ◽  
Saturation Mutagenesis ◽  
Sequence Specificity ◽  
Rich Region ◽  
Finger Protein ◽  
Gc Box

MIG1 is a zinc finger protein that mediates glucose repression in the yeast Saccharomyces cerevisiae. MIG1 is related to the mammalian Krox/Egr, Wilms' tumor, and Sp1 finger proteins. It has two fingers and binds to a GCGGGG motif that resembles the GC boxes recognized by these mammalian proteins. We have performed a complete saturation mutagenesis of a natural MIG1 site in order to elucidate its binding specificity. We found that only three mutations within the GC box retain the ability to bind MIG1: G1 to C, C2 to T, and G5 to A. This result is consistent with current models for zinc finger-DNA binding, which assume that the sequence specificity is determined by base triplet recognition within the GC box. Surprisingly, we found that an AT-rich region 5' to the GC box also is important for MIG1 binding. This AT box is present in all natural MIG1 sites, and it is protected by MIG1 in DNase I footprints. However, the AT box differs from the GC box in that no single base within it is essential for binding. Instead, the AT-rich nature of this sequence seems to be crucial. The fact that AT-rich sequences are known to increase DNA flexibility prompted us to test whether MIG1 bends DNA. We found that binding of MIG1 is associated with bending within the AT box. We conclude that DNA binding by a simple zinc finger protein such as MIG1 can involve both recognition of the GC box and flanking sequence preferences that may reflect local DNA bendability.

scholarly journals Structural view on the role of WT1’s zinc finger 1 in DNA binding

2018 ◽  
Author(s):  
Raymond K. Yengo ◽  
Elmar Nurmemmedov ◽  
Marjolein M Thunnissen
Keyword(s):  
Dna Binding ◽  
Zinc Finger ◽  
Zinc Fingers ◽  
Binding Specificity ◽  
Regulatory Elements ◽  
Regulatory Function ◽  
Gene Promoters ◽  
Binding Behavior ◽  
Dna Binding Specificity

AbstractThe WT1 protein is a transcription factor that controls genes involved in cell proliferation, differentiation and apoptosis. It has become increasing apparent that WT1 can act both as a tumor suppressor and oncogene in a tissue specific manner. This opposing role of WT1 is linked to its underlying transcriptional regulatory function, which involves the specific binding to its regulatory elements on gene promoters. WT1 binds DNA using it C-terminal domain made up of 4 C2H2-typ zinc fingers. This same zinc finger domain is used to bind RNA and proteins and it is still not clear how each zinc finger contributes to this promiscuous binding behavior. The molecular details of DNA binding by zinc finger 2 to 4 have been described but it remains to be determined whether or not zinc finger 1 binds DNA and if so whether it exhibits any DNA binding specificity. We present the X-ray structures of zinc finger 1 to 3 bound to a 9 bp and an 8 bp DNA. The two structures refined to 1.7 Å, show no DNA binding specificity for zinc finger 1. The only DNA interactions involving zinc finger 1 are crystal-packing interactions with a symmetry related molecule. In the structure of zinc finger 1 to 3 bound to the 9 bp DNA we observe a shift in the DNA binding positions for zinc fingers 2 and 3. These structures provide molecular detail into the WT1-DNA interaction showing that zinc finger 1 only modestly contributes to DNA binding affinity through transient interactions. The dislocation of zinc finger 2 and 3 emphasizes the importance of zinc finger 4 for maintaining gene transcriptional specificity.

The giant gene of Drosophila encodes a b-ZIP DNA-binding protein that regulates the expression of other segmentation gap genes

Development ◽  
1992 ◽  
Vol 114 (1) ◽  
pp. 99-112 ◽  
Author(s):  
M. Capovilla ◽  
E.D. Eldon ◽  
V. Pirrotta
Keyword(s):  
Dna Binding ◽  
Leucine Zipper ◽  
Ectopic Expression ◽  
Regulatory Elements ◽  
In Vitro Translation ◽  
Gap Genes ◽  
Zip Family ◽  
Negative Effect ◽  
Drosophila Embryos

The sequence of a cDNA from the giant gene of Drosophila shows that its product has a basic domain followed by a leucine zipper motif. Both features contain characteristic conserved elements of the b-ZIP family of DNA-binding proteins. Expression of the gene in bacteria or by in vitro translation yields a protein that migrates considerably faster than the protein extracted from Drosophila embryos. Treatment with phosphatase shows that this difference is due to multiple phosphorylation of the giant protein in the embryo. Ectopic expression of the protein in precellular blastoderm embryos produces abnormal phenotypes with a pattern of segment loss closely resembling that of Kruppel mutant embryos. Immunological staining shows that giant, ectopically expressed from the hsp70 promoter, represses the expression of both the Kruppel and knirps segmentation gap genes. The analysis of the interactions between Kruppel, knirps and giant reveals a network of negative regulation. We show that the apparent positive regulation of knirps by Kruppel is in fact mediated by a negative effect of Kruppel on giant and a negative effect of giant on knirps. giant protein made in bacteria or in embryos binds in vitro to the Kruppel regulatory elements CD1 and CD2 and recognizes a sequence resembling the binding sites of other b-ZIP proteins.

scholarly journals Importance of a flanking AT-rich region in target site recognition by the GC box-binding zinc finger protein MIG1.

1994 ◽  
Vol 14 (3) ◽  
pp. 1979-1985 ◽  
Author(s):  
M Lundin ◽  
J O Nehlin ◽  
H Ronne
Keyword(s):  
Dna Binding ◽  
Zinc Finger ◽  
Zinc Finger Protein ◽  
Wilms Tumor ◽  
Glucose Repression ◽  
Saturation Mutagenesis ◽  
Sequence Specificity ◽  
Rich Region ◽  
Finger Protein ◽  
Gc Box

MIG1 is a zinc finger protein that mediates glucose repression in the yeast Saccharomyces cerevisiae. MIG1 is related to the mammalian Krox/Egr, Wilms' tumor, and Sp1 finger proteins. It has two fingers and binds to a GCGGGG motif that resembles the GC boxes recognized by these mammalian proteins. We have performed a complete saturation mutagenesis of a natural MIG1 site in order to elucidate its binding specificity. We found that only three mutations within the GC box retain the ability to bind MIG1: G1 to C, C2 to T, and G5 to A. This result is consistent with current models for zinc finger-DNA binding, which assume that the sequence specificity is determined by base triplet recognition within the GC box. Surprisingly, we found that an AT-rich region 5' to the GC box also is important for MIG1 binding. This AT box is present in all natural MIG1 sites, and it is protected by MIG1 in DNase I footprints. However, the AT box differs from the GC box in that no single base within it is essential for binding. Instead, the AT-rich nature of this sequence seems to be crucial. The fact that AT-rich sequences are known to increase DNA flexibility prompted us to test whether MIG1 bends DNA. We found that binding of MIG1 is associated with bending within the AT box. We conclude that DNA binding by a simple zinc finger protein such as MIG1 can involve both recognition of the GC box and flanking sequence preferences that may reflect local DNA bendability.

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