Zinc-binding and protein-protein interactions mediated by the polyomavirus large T antigen zinc finger.

Polyomavirus large T antigen binds to two sites located between positions -110 and -170 of a human heat shock protein 70 (hsp70) promoter. Methylation interference studies show that binding for each site is determined by two GPuGGC pentanucleotide sequences. The specificity of this binding interaction is similar to that observed for large T binding to the viral genome. The existence of sequences that bind a viral protein in a cellular promoter raises the possibility that these sequences play a role in gene expression in an uninfected cell. We show that hsp70 large T antigen binding site 1 is capable of functioning as an upstream promoter element in cells that do not contain any viral T antigen. Genetic analysis of this effect suggests that a cellular factor exists that has a binding specificity that overlaps but is not identical to that of polyomavirus large T antigen. To determine whether binding of polyomavirus large T antigen can regulate expression of the intact human hsp70 promoter, we have introduced the promoter into mouse cells with plasmids that express the polyomavirus early proteins. These proteins stimulate the level of correctly initiated hsp70 transcripts, but surprisingly the degree of stimulation remains unchanged for promoter constructs in which the large T antigen binding sites have been deleted. These observations suggest that trans activation of the hsp70 promoter by the polyomavirus early proteins occurs through protein-protein interactions and not through sequence-specific DNA binding.

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Ras Transformation Overrides a Proliferation Defect Induced by Tpm3.1 Knockout

Cellular & Molecular Biology Letters ◽

10.1515/cmble-2015-0037 ◽

2015 ◽

Vol 20 (4) ◽

Cited By ~ 5

Author(s):

Jason D. Coombes ◽

Galina Schevzov ◽

Chin-Yi Kan ◽

Carlotta Petti ◽

Michelle F. Maritz ◽

...

Keyword(s):

Growth Factor ◽

Actin Cytoskeleton ◽

Cancer Cells ◽

Protein Interactions ◽

Retroviral Vectors ◽

Transformation Process ◽

T Antigen ◽

Large T Antigen ◽

Ras Gene ◽

Sv40 Large T Antigen

AbstractExtensive re-organisation of the actin cytoskeleton and changes in the expression of its binding proteins is a characteristic feature of cancer cells. Previously we have shown that the tropomyosin isoform Tpm3.1, an integral component of the actin cytoskeleton in tumor cells, is required for tumor cell survival. Our objective was to determine whether cancer cells devoid of Tpm3.1 would evade the tumorgenic effects induced by H-Ras transformation. The tropomyosin isoform (Tpm) expression profile of a range of cancer cell lines (21) demonstrates that Tpm3.1 is one of the most broadly expressed Tpm isoform. Consequently, the contribution of Tpm3.1 to the transformation process was functionally evaluated. Primary embryonic fibroblasts isolated from wild type (WT) and Tpm3.1 knockout (KO) mice were transduced with retroviral vectors expressing SV40 large T antigen and an oncogenic allele of the H-Ras gene, H-RasV12, to generate immortalized and transformed WT and KO MEFs respectively. We show that Tpm3.1 is required for growth factor-independent proliferation in the SV40 large T antigen immortalized MEFs, but this requirement is overcome by H-Ras transformation. Consistent with those findings, we found that Tpm3.1 was not required for anchorage independent growth or growth of H-Ras-driven tumors in a mouse model. Finally, we show that pERK and Importin 7 protein interactions are significantly decreased in the SV40 large T antigen immortalized KO MEFs but not in the H-Ras transformed KO cells, relative to control MEFs. The data demonstrate that H-Ras transformation overrides a requirement for Tpm3.1 in growth factor-independent proliferation of immortalized MEFs. We propose that in the SV40 large T antigen immortalized MEFs, Tpm3.1 is partly responsible for the efficient interaction between pERK and Imp7 resulting in cell proliferation, but this is overidden by Ras transformation.

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The Simian Virus 40 Core Origin Contains Two Separate Sequence Modules That Support T-Antigen Double-Hexamer Assembly

Journal of Virology ◽

10.1128/jvi.74.18.8589-8600.2000 ◽

2000 ◽

Vol 74 (18) ◽

pp. 8589-8600 ◽

Cited By ~ 17

Author(s):

K. R. Sreekumar ◽

Andrea E. Prack ◽

Danielle R. Winters ◽

Brett A. Barbaro ◽

Peter A. Bullock

Keyword(s):

Protein Interactions ◽

Simian Virus 40 ◽

Simian Virus ◽

T Antigen ◽

Protein Protein Interactions ◽

Rich Region ◽

Subsequent Formation ◽

Sv40 Origin ◽

Additional Protein ◽

Assembly Unit

ABSTRACT Using subfragments of the simian virus 40 (SV40) core origin, we demonstrate that two alternative modules exist for the assembly of T-antigen (T-ag) double hexamers. Pentanucleotides 1 and 3 and the early palindrome (EP) constitute one assembly unit, while pentanucleotides 2 and 4 and the AT-rich region constitute a second, relatively weak, assembly unit. Related studies indicate that on the unit made up of pentanucleotide 1 and 3 and the EP assembly unit, the first hexamer forms on pentanucleotide 1 and that owing to additional protein-DNA and protein-protein interactions, the second hexamer is able to form on pentanucleotide 3. Oligomerization on the unit made up of pentanucleotide 2 and 4 and the AT-rich region is initiated by assembly of a hexamer on pentanucleotide 4; subsequent formation of the second hexamer takes place on pentanucleotide 2. Given that oligomerization on the SV40 origin is limited to double-hexamer formation, it is likely that only a single module is used for the initial assembly of T-ag double hexamers. Finally, we discuss the evidence that nucleotide hydrolysis is required for the remodeling events that result in the utilization of the second assembly unit.

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Self-association of the erythroid transcription factor GATA-1 mediated by its zinc finger domains.

Molecular and Cellular Biology ◽

10.1128/mcb.15.5.2448 ◽

1995 ◽

Vol 15 (5) ◽

pp. 2448-2456 ◽

Cited By ~ 122

Author(s):

M Crossley ◽

M Merika ◽

S H Orkin

Keyword(s):

Transcription Factors ◽

Dna Binding ◽

Zinc Finger ◽

Protein Interactions ◽

Physical Interaction ◽

Erythroid Cells ◽

Protein Protein Interactions ◽

Self Association ◽

Zinc Finger Region ◽

In Erythroid Cells

GATA-1, the founding member of a distinctive family of transcription factors, is expressed predominantly in erythroid cells and participates in the expression of numerous erythroid cell-expressed genes. GATA-binding sites are found in the promoters and enhancers of globin and nonglobin erythroid genes as well as in the alpha- and beta-globin locus control regions. To elucidate how GATA-1 may function in a variety of regulatory contexts, we have examined its protein-protein interactions. Here we show that GATA-1 self-associates in solution and in whole-cell extracts and that the zinc finger region of the molecule is sufficient to mediate this interaction. This physical interaction can influence transcription, as GATA-1 self-association is able to recruit a transcriptionally active but DNA-binding-defective derivative of GATA-1 to promoter-bound GATA-1 and result in superactivation. Through in vitro studies with bacterially expressed glutathione S-transferase fusion proteins, we have localized the minimal domain required for GATA-1 self-association to 40 amino acid residues within the C-terminal zinc finger region. Finally, we have detected physical interaction of GATA-1 with other GATA family members (GATA-2 and GATA-3) also mediated through the zinc finger domain. These findings have broad implications for the involvement of GATA factors in transcriptional control. In particular, the interaction of GATA-1 with itself and with other transcription factors may facilitate its function at diverse promoters in erythroid cells and also serve to bring together, or stabilize, loops between distant regulatory elements, such as the globin locus control regions and downstream globin promoters. We suggest that the zinc finger region of GATA-1, and related proteins, is multifunctional and mediates not only DNA binding but also important protein-protein interactions.

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LMCD1/Dyxin Is a Novel Transcriptional Cofactor That Restricts GATA6 Function by Inhibiting DNA Binding

Molecular and Cellular Biology ◽

10.1128/mcb.25.20.8864-8873.2005 ◽

2005 ◽

Vol 25 (20) ◽

pp. 8864-8873 ◽

Cited By ~ 44

Author(s):

Nibedita Rath ◽

Zhishan Wang ◽

Min Min Lu ◽

Edward E. Morrisey

Keyword(s):

Dna Binding ◽

Zinc Finger ◽

Protein Interactions ◽

Cardiac Tissue ◽

Protein Protein Interactions ◽

Mobility Shift ◽

Gata Factors ◽

Lim Proteins ◽

High Level ◽

Carboxy Terminal

ABSTRACT The activity of GATA factors is regulated, in part, at the level of protein-protein interactions. LIM domain proteins, first defined by the zinc finger motifs found in the Lin11, Isl-1, and Mec-3 proteins, act as coactivators of GATA function in both hematopoietic and cardiovascular tissues. We have identified a novel GATA-LIM interaction between GATA6 and LMCD1/dyxin. The LIM domains and cysteine-rich domains in LMCD1/dyxin and the carboxy-terminal zinc finger of GATA6 mediate this interaction. Expression of LMCD1/dyxin is remarkably similar to that of GATA6, with high-level expression observed in distal airway epithelium of the lung, vascular smooth muscle, and myocardium. In contrast to other GATA-LIM protein interactions, LMCD1/dyxin represses GATA6 activation of both lung and cardiac tissue-specific promoters. Electrophoretic mobility shift and chromatin immunoprecipitation assays show that LMCD1/dyxin represses GATA6 function by inhibiting GATA6 DNA binding. These data reveal an interaction between GATA6 and LMCD1/dyxin and demonstrate a novel mechanism through which LIM proteins can assert their role as transcriptional cofactors of GATA proteins.

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ZNF224 Protein: Multifaceted Functions Based on Its Molecular Partners

Molecules ◽

10.3390/molecules26206296 ◽

2021 ◽

Vol 26 (20) ◽

pp. 6296

Author(s):

Elena Cesaro ◽

Angelo Lupo ◽

Roberta Rapuano ◽

Arianna Pastore ◽

Michela Grosso ◽

...

Keyword(s):

Dna Binding ◽

Zinc Finger ◽

Protein Interactions ◽

Transcriptional Repression ◽

Zinc Finger Protein ◽

Current Knowledge ◽

Protein Protein Interactions ◽

Multifunctional Protein ◽

Finger Protein ◽

Zinc Finger Domains

The transcription factor ZNF224 is a Kruppel-like zinc finger protein that consists of 707 amino acids and contains 19 tandemly repeated C2H2 zinc finger domains that mediate DNA binding and protein–protein interactions. ZNF224 was originally identified as a transcriptional repressor of genes involved in energy metabolism, and it was demonstrated that ZNF224-mediated transcriptional repression needs the interaction of its KRAB repressor domain with the co-repressor KAP1 and its zinc finger domains 1–3 with the arginine methyltransferase PRMT5. Furthermore, the protein ZNF255 was identified as an alternative isoform of ZNF224 that possesses different domain compositions mediating distinctive functional interactions. Subsequent studies showed that ZNF224 is a multifunctional protein able to exert different transcriptional activities depending on the cell context and the variety of its molecular partners. Indeed, it has been shown that ZNF224 can act as a repressor, an activator and a cofactor for other DNA-binding transcription factors in different human cancers. Here, we provide a brief overview of the current knowledge on the multifaceted interactions of ZNF224 and the resulting different roles of this protein in various cellular contexts.

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