scholarly journals Identification of downstream-initiated c-Myc proteins which are dominant-negative inhibitors of transactivation by full-length c-Myc proteins.

1997 ◽  
Vol 17 (3) ◽  
pp. 1459-1468 ◽  
Author(s):  
G D Spotts ◽  
S V Patel ◽  
Q Xiao ◽  
S R Hann
Keyword(s):  
Dominant Negative ◽  
Full Length ◽  
Transactivation Domain ◽  
Translational Initiation ◽  
Dna Binding Domains ◽  
Cellular Processes ◽  
Binding Domains ◽  
Inhibitory Function ◽  
Myc Gene ◽  
S Proteins

The c-myc gene has been implicated in multiple cellular processes including proliferation, differentiation, and apoptosis. In addition to the full-length c-Myc 1 and 2 proteins, we have found that human, murine, and avian cells express smaller c-Myc proteins arising from translational initiation at conserved downstream AUG codons. These c-Myc short (c-Myc S) proteins lack most of the N-terminal transactivation domain but retain the C-terminal protein dimerization and DNA binding domains. As with full-length c-Myc proteins, the c-Myc S proteins appear to be localized to the nucleus, are relatively unstable, and are phosphorylated. Significant levels of c-Myc S, often approaching the levels of full-length c-Myc, are transiently observed during the rapid growth phase of several different types of cells. Optimization of the upstream initiation codons resulted in greatly reduced synthesis of the c-Myc S proteins, suggesting that a "leaky scanning" mechanism leads to the translation of these proteins. In some hematopoietic tumor cell lines having altered c-myc genes, the c-Myc S proteins are constitutively expressed at levels equivalent to that of full-length c-Myc. As predicted, the c-Myc S proteins are unable to activate transcription and inhibited transactivation by full-length c-Myc proteins, suggesting a dominant-negative inhibitory function. While these transcriptional inhibitors would not be expected to function as full-length c-Myc, the occurrence of tumors which express constitutive high levels of c-Myc S and their transient synthesis during rapid cell growth suggest that these proteins do not interfere with the growth-promoting functions of full-length c-Myc.

Ligand-independent activation of oestrogen receptor α by caveolin-1

2001 ◽  
Vol 359 (1) ◽  
pp. 203-210 ◽  
Author(s):  
Amnon SCHLEGEL ◽  
Chenguang WANG ◽  
Richard G. PESTELL ◽  
Michael P. LISANTI
Keyword(s):  
Transcriptional Activation ◽  
Oestrogen Receptor ◽  
Activation Function ◽  
Binding Domain ◽  
Mammary Adenocarcinoma ◽  
Transactivation Domain ◽  
Caveolin 1 ◽  
Dna Binding Domains ◽  
Binding Domains ◽  
Oestrogen Receptor Α

Expression of caveolin-1 in the human mammary adenocarcinoma cell line MCF-7 causes ligand-independent concentration of oestrogen receptor α (ERα) in the nucleus, and potentiates ligand-independent and ligand-dependent transcription from an oestrogen response element-driven reporter gene. Furthermore, caveolin-1 co-immunoprecipitates with ERα [Schlegel, Wang, Katzenellenbogen, Pestell and Lisanti (1999) J. Biol. Chem. 274, 33551–33556]. In the present study we show that caveolin-1 binds directly to ERα. This interaction is mediated by residues 82–101 of caveolin-1 (i.e. the caveolin scaffolding domain) and residues 1–282 of ERα. The caveolin-binding domain of ERα includes the ligand-independent transactivation domain, activation function (AF)-1, but lacks the hormone-binding domain and the ligand-gated transactivation domain, AF-2. In co-transfection studies, caveolin-1 potentiates the transcriptional activation of ERα(1–282), a truncation mutant that has intact AF-1 and DNA-binding domains. Since AF-1 activity is regulated largely by phosphorylation we determined that co-expression with caveolin-1 increased the basal phosphorylation of ERα(1–282), but blocked the epidermal growth factor-dependent increase in phosphorylation. Indeed, caveolin-1 interacted with and potentiated the transactivation of an ERα mutant that cannot be phosphorylated by extracellular signal-regulated kinase (ERK)1/2 [ERα(Ser118 → Ala)]. Thus caveolin-1 is a novel ERα regulator that drives ERK1/2-independent phosphorylation and activation of AF-1.

scholarly journals BSAP Can Repress Enhancer Activity by Targeting PU.1 Function

2000 ◽  
Vol 20 (6) ◽  
pp. 1911-1922 ◽  
Author(s):  
Shanak Maitra ◽  
Michael Atchison
Keyword(s):  
Transcription Factors ◽  
Cell Differentiation ◽  
Dna Binding ◽  
B Cell ◽  
Transactivation Domain ◽  
B Cell Differentiation ◽  
Developmentally Regulated ◽  
Enhancer Activity ◽  
Dna Binding Domains ◽  
Binding Domains

ABSTRACT PU.1 and BSAP are transcription factors crucial for proper B-cell development. Absence of PU.1 results in loss of B, T, and myeloid cells, while absence of BSAP results in an early block in B-cell differentiation. Both of these proteins bind to the immunoglobulin κ chain 3′ enhancer, which is developmentally regulated during B-cell differentiation. We find here that BSAP can repress 3′ enhancer activity. This repression can occur in plasmacytoma lines or in a non-B-cell line in which the enhancer is activated by addition of the appropriate enhancer binding transcription factors. We show that the transcription factor PU.1 is a target of the BSAP-mediated repression. Although PU.1 and BSAP can physically interact through their respective DNA binding domains, this interaction does not affect DNA binding. When PU.1 function is assayed in isolation on a multimerized PU.1 binding site, BSAP targets a portion of the PU.1 transactivation domain (residues 7 to 30) for repression. The BSAP inhibitory domain (residues 358 to 385) is needed for this repression. Interestingly, the coactivator protein p300 can eliminate this BSAP-mediated repression. We also show that PU.1 can inhibit BSAP transactivation and that this repression requires PU.1 amino acids 7 to 30. Transfection of p300 resulted in only a partial reversal of PU.1-mediated repression of BSAP. When PU.1 function is assayed in the context of the immunoglobulin κ chain 3′ enhancer and associated binding proteins, BSAP represses PU.1 function by a distinct mechanism. This repression does not require the PU.1 transactivation or PEST domains and cannot be reversed by p300 expression. The possible roles of BSAP and PU.1 antagonistic activities in hematopoietic development are discussed.

scholarly journals Complex Functions of AP-1 Transcription Factors in Differentiation and Survival of PC12 Cells

2001 ◽  
Vol 21 (13) ◽  
pp. 4369-4378 ◽  
Author(s):  
Sirpa Leppä ◽  
Minna Eriksson ◽  
Rainer Saffrich ◽  
Wilhelm Ansorge ◽  
Dirk Bohmann
Keyword(s):  
Dna Binding ◽  
Neuronal Differentiation ◽  
Pc12 Cells ◽  
Protective Role ◽  
Transactivation Domain ◽  
Dna Binding Domains ◽  
Binding Domains ◽  
Before And After ◽  
Mitogen Activated Protein ◽  
Neurite Formation

ABSTRACT c-Jun activation by mitogen-activated protein kinases has been implicated in various cellular signal responses. We investigated how JNK and c-Jun contribute to neuronal differentiation, cell survival, and apoptosis. In differentiated PC12 cells, JNK signaling can induce apoptosis and c-Jun mediates this response. In contrast, we show that in PC12 cells that are not yet differentiated, the AP-1 family member ATF-2 and not c-Jun acts as an executor of apoptosis. In this context c-Jun expression protects against apoptosis and triggers neurite formation. Thus, c-Jun has opposite functions before and after neuronal differentiation. These findings suggest a model in which the balance between ATF-2 and Jun activity in PC12 cells governs the choice between differentiation towards a neuronal fate and an apoptotic program. Further analysis of c-Jun mutants showed that the differentiation response requires functional dimerization and DNA-binding domains and that it is stimulated by phosphorylation in the transactivation domain. In contrast, c-Jun mutants incompetent for DNA binding or dimerization and also mutants lacking JNK binding and phosphorylation sites that cannot elicit neuronal differentiation efficiently protect PC12 cells from apoptosis. Hence, the protective role of c-Jun appears to be mediated by an unconventional mechanism that is separable from its function as a classical AP-1 transcription factor.

scholarly journals Two high-mobility group box domains act together to underwind and kink DNA

2015 ◽  
Vol 71 (7) ◽  
pp. 1423-1432 ◽  
Author(s):  
R. Sánchez-Giraldo ◽  
F. J. Acosta-Reyes ◽  
C. S. Malarkey ◽  
N. Saperas ◽  
M. E. A. Churchill ◽  
...  
Keyword(s):  
High Mobility ◽  
High Mobility Group ◽  
Sequence Specificity ◽  
High Mobility Group Protein ◽  
Dna Binding Domains ◽  
Cellular Processes ◽  
Binding Domains ◽  
Group Protein ◽  
A Domains ◽  
Architectural Factor

High-mobility group protein 1 (HMGB1) is an essential and ubiquitous DNA architectural factor that influences a myriad of cellular processes. HMGB1 contains two DNA-binding domains, box A and box B, which have little sequence specificity but have remarkable abilities to underwind and bend DNA. Although HMGB1 box A is thought to be responsible for the majority of HMGB1–DNA interactions with pre-bent or kinked DNA, little is known about how it recognizes unmodified DNA. Here, the crystal structure of HMGB1 box A bound to an AT-rich DNA fragment is reported at a resolution of 2 Å. Two box A domains of HMGB1 collaborate in an unusual configuration in which the Phe37 residues of both domains stack together and intercalate the same CG base pair, generating highly kinked DNA. This represents a novel mode of DNA recognition for HMGB proteins and reveals a mechanism by which structure-specific HMG boxes kink linear DNA.

Ikaros 6 Immortalizes Murine Hematopoietic Precursors In Vitro.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 4354-4354
Author(s):  
Anna Ruiz ◽  
Hugh J.M. Brady
Keyword(s):  
Dna Binding ◽  
Transcriptional Activation ◽  
Zinc Finger Protein ◽  
Dominant Negative ◽  
In Vitro Assays ◽  
Dna Binding Domains ◽  
Binding Domains ◽  
Delayed Cell Death

Abstract The Ikaros transcription factor has been shown to play an important role in the differentiation of both the myeloid and lymphoid lineages. The ikaros gene encodes for a zinc finger protein containing seven exons that can be alternatively spliced generating several isoforms with differing functional properties. Isoforms with less than three DNA binding domains act as dominant negative (DN) by forming complexes with longer isoforms and interfering with their DNA binding and transcriptional activation ability. Mice heterozygous for a DN ikaros isoform develop T cell leukemia and lymphoma with 100% penetrance. Overexpression of DN Ikaros isoforms has been found in some forms of leukemias. We have previously reported overexpression of the DN Ikaros6 (Ik6) isoform in a subset of leukemia patients harboring t(4;11) translocations. In addition, we inducibly expressed Ik6 in BaF3 cells and found that Ik6 overexpression delayed cell death after IL-3 withdrawal. To further investigate the leukemogenic properties of Ik6 overexpression, we have transduced murine hematopoietic precursors with a retroviral Ik6 expression vector and have analysed the effects on proliferation and differentiation of these precursors by in vitro colony formation assays. We have found that Ik6 can immortalize murine hematopopietic precursors in these in vitro assays. We are currently analysing the leukemogenic potential of Ik6 in vivo by transplanting Ik6 expressing cell lines into NOD/SCID mice.

Multiple protein functions of paired in Drosophila development and their conservation in the Gooseberry and Pax3 homologs

Development ◽  
2001 ◽  
Vol 128 (3) ◽  
pp. 395-405
Author(s):  
L. Xue ◽  
X. Li ◽  
M. Noll
Keyword(s):  
Male Fertility ◽  
Transactivation Domain ◽  
Dna Binding Domains ◽  
Coding Regions ◽  
Binding Domains ◽  
Spatiotemporal Expression ◽  
C Terminus ◽  
Multiple Protein ◽  
Protein Functions ◽  
Cuticle Development

The Drosophila segmentation gene paired, whose product is homologous to the Drosophila Gooseberry and mammalian Pax3 proteins, has three general functions: proper development of the larval cuticle, survival to adulthood and male fertility. Both DNA-binding domains, the conserved N-terminal paired-domain and prd-type homeodomain, are required within the same molecule for all general paired functions, whereas a conserved His-Pro repeat located near its C terminus is a transactivation domain potentiating these functions. The C-terminal moiety of Paired includes two additional functional motifs: one, also present in Gooseberry and Pax3, is required for segmentation and cuticle development; the other, retained only in Gooseberry, is necessary for survival. The male fertility function, which cannot be replaced by Gooseberry and Pax3, is specified by the conserved N-terminal rather than the divergent C-terminal moiety of Paired. We conclude that the functional diversification of paired, gooseberry and Pax3, primarily determined by variations in their enhancers, is modified by adaptations of their coding regions as a necessary consequence of their newly acquired spatiotemporal expression.

CASP, a novel, highly conserved alternative-splicing product of the CDP/cut/cux gene, lacks cut-repeat and homeo DNA-binding domains, and interacts with full-length CDP in vitro

Gene ◽  
1997 ◽  
Vol 197 (1-2) ◽  
pp. 73-81 ◽  
Author(s):  
Patricia M J. Lievens ◽  
Cristina Tufarelli ◽  
Janae J Donady ◽  
Amy Stagg ◽  
Ellis J. Neufeld
Keyword(s):  
Alternative Splicing ◽  
Dna Binding ◽  
Full Length ◽  
Dna Binding Domains ◽  
Binding Domains

scholarly journals In SilicoAnalysis for Transcription Factors WithZn(II)2C6Binuclear Cluster DNA-Binding Domains inCandida albicans

2005 ◽  
Vol 6 (7-8) ◽  
pp. 345-356 ◽  
Author(s):  
Sergi Maicas ◽  
Inmaculada Moreno ◽  
Almudena Nieto ◽  
Micaela Gómez ◽  
Rafael Sentandreu ◽  
...  
Keyword(s):  
Transcription Factors ◽  
Open Reading Frames ◽  
Multi Drug Resistance ◽  
Dna Binding Domains ◽  
Cellular Processes ◽  
Zinc Cluster ◽  
Binding Domains ◽  
Wide Range ◽  
Localization Signal ◽  
Transcription Regulators

A total of 6047 open reading frames in theCandida albicansgenome were screened forZn(II)2C6-type zinc cluster proteins (or binuclear cluster proteins) involved in DNA recognition. These fungal proteins are transcription regulators of genes involved in a wide range of cellular processes, including metabolism of different compounds such as sugars or amino acids, as well as multi-drug resistance, control of meiosis, cell wall architecture, etc. The selection criteria used in the sequence analysis were the presence of theCysX2CysX6CysX5-16CysX2CysX6-8Cysmotif and a putative nuclear localization signal. Using this approach, 70 putativeZn(II)2C6transcription factors have been found in the genome ofC. albicans.

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