scholarly journals trans-dominant mutants of E1A provide genetic evidence that the zinc finger of the trans-activating domain binds a transcription factor.

1991 ◽  
Vol 11 (9) ◽  
pp. 4287-4296 ◽  
Author(s):  
L C Webster ◽  
R P Ricciardi
Keyword(s):  
Transcription Factor ◽  
Zinc Finger ◽  
Cellular Protein ◽  
Site Directed Mutagenesis ◽  
Cellular Transcription Factor ◽  
Dominant Phenotype ◽  
Cellular Genes ◽  
Critical Residue ◽  
The Individual ◽  
Cellular Transcription

The 289R E1A protein of adenovirus stimulates transcription of early viral and certain cellular genes. trans-Activation requires residues 140 to 188, which encompass a zinc finger. Several studies have indicated that trans-activation by E1A is mediated through cellular transcription factors. In particular, the ability of the trans-dominant E1A point mutant hr5 (Ser-185 to Asn) to inhibit wild-type E1A trans-activation was proposed to result from the sequestration of a cellular factor. Using site-directed mutagenesis, we individually replaced every residue within and flanking the trans-activating domain with a conservative amino acid, revealing 16 critical residues. Six of the individual substitutions lying in a contiguous stretch C terminal to the zinc finger (carboxyl region183-188) imparted a trans-dominant phenotype. trans-Dominance was even produced by deletion of the entire carboxyl region183-188. Conversely, an intact finger region147-177 was absolutely required for trans-dominance, since second-site substitution of every critical residue in this region abrogated the trans-dominant phenotype of the hr5 protein. These data indicate that the finger region147-177 bind a limiting cellular transcription factor and that the carboxyl region183-188 provides a separate and essential function. In addition, we show that four negatively charged residues within the trans-activating domain do not comprise a distinct acidic activating region. We present a model in which the trans-activating domain of E1A binds to two different cellular protein targets through the finger and carboxyl regions.

trans-dominant mutants of E1A provide genetic evidence that the zinc finger of the trans-activating domain binds a transcription factor

1991 ◽  
Vol 11 (9) ◽  
pp. 4287-4296
Author(s):  
L C Webster ◽  
R P Ricciardi
Keyword(s):  
Transcription Factor ◽  
Zinc Finger ◽  
Cellular Protein ◽  
Site Directed Mutagenesis ◽  
Cellular Transcription Factor ◽  
Dominant Phenotype ◽  
Cellular Genes ◽  
Critical Residue ◽  
The Individual ◽  
Cellular Transcription

The 289R E1A protein of adenovirus stimulates transcription of early viral and certain cellular genes. trans-Activation requires residues 140 to 188, which encompass a zinc finger. Several studies have indicated that trans-activation by E1A is mediated through cellular transcription factors. In particular, the ability of the trans-dominant E1A point mutant hr5 (Ser-185 to Asn) to inhibit wild-type E1A trans-activation was proposed to result from the sequestration of a cellular factor. Using site-directed mutagenesis, we individually replaced every residue within and flanking the trans-activating domain with a conservative amino acid, revealing 16 critical residues. Six of the individual substitutions lying in a contiguous stretch C terminal to the zinc finger (carboxyl region183-188) imparted a trans-dominant phenotype. trans-Dominance was even produced by deletion of the entire carboxyl region183-188. Conversely, an intact finger region147-177 was absolutely required for trans-dominance, since second-site substitution of every critical residue in this region abrogated the trans-dominant phenotype of the hr5 protein. These data indicate that the finger region147-177 bind a limiting cellular transcription factor and that the carboxyl region183-188 provides a separate and essential function. In addition, we show that four negatively charged residues within the trans-activating domain do not comprise a distinct acidic activating region. We present a model in which the trans-activating domain of E1A binds to two different cellular protein targets through the finger and carboxyl regions.

scholarly journals HIV-1 Tat Recruits HDM2 E3 Ligase To Target IRF-1 for Ubiquitination and Proteasomal Degradation

mBio ◽  
2016 ◽  
Vol 7 (5) ◽  
Author(s):  
Anna Lisa Remoli ◽  
Giulia Marsili ◽  
Edvige Perrotti ◽  
Chiara Acchioni ◽  
Marco Sgarbanti ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Immune Responses ◽  
Cellular Protein ◽  
Cellular Targets ◽  
Host Immune Responses ◽  
Cellular Transcription Factor ◽  
Regulatory Circuit ◽  
Mechanistic Basis ◽  
Cellular Transcription ◽  
Hiv 1

ABSTRACTIn addition to its ability to regulate HIV-1 promoter activation, the viral transactivator Tat also functions as a determinant of pathogenesis and disease progression by directly and indirectly modulating the host anti-HIV response, largely through the capacity of Tat to interact with and modulate the activities of multiple host proteins. We previously demonstrated that Tat modulated both viral and host transcriptional machinery by interacting with the cellular transcription factor interferon regulatory factor 1 (IRF-1). In the present study, we investigated the mechanistic basis and functional significance of Tat−IRF-1 interaction and demonstrate that Tat dramatically decreased IRF-1 protein stability. To accomplish this, Tat exploited the cellular HDM2 (human double minute 2 protein) ubiquitin ligase to accelerate IRF-1 proteasome-mediated degradation, resulting in a quenching of IRF-1 transcriptional activity during HIV-1 infection. These data identify IRF-1 as a new target of Tat-induced modulation of the cellular protein machinery and reveal a new strategy developed by HIV-1 to evade host immune responses.IMPORTANCECurrent therapies have dramatically reduced morbidity and mortality associated with HIV infection and have converted infection from a fatal pathology to a chronic disease that is manageable via antiretroviral therapy. Nevertheless, HIV-1 infection remains a challenge, and the identification of useful cellular targets for therapeutic intervention remains a major goal. The cellular transcription factor IRF-1 impacts various physiological functions, including the immune response to viral infection. In this study, we have identified a unique mechanism by which HIV-1 evades IRF-1-mediated host immune responses and show that the viral protein Tat accelerates IRF-1 proteasome-mediated degradation and inactivates IRF-1 function. Restoration of IRF-1 functionality may thus be regarded as a potential strategy to reinstate both a direct antiviral response and a more broadly acting immune regulatory circuit.

scholarly journals Expression of c-jun during macrophage differentiation of HL-60 cells

Blood ◽  
1991 ◽  
Vol 77 (12) ◽  
pp. 2618-2623 ◽  
Author(s):  
R Gaynor ◽  
K Simon ◽  
P Koeffler
Keyword(s):  
Leukemia Cell ◽  
Early Response ◽  
Cellular Growth ◽  
Myelogenous Leukemia ◽  
Leukemia Cell Line ◽  
Northern Analysis ◽  
Macrophage Differentiation ◽  
Cellular Transcription Factor ◽  
Cellular Genes ◽  
Cellular Transcription

Abstract Cellular transcription factors are important in the regulation of cellular genes. Recent studies have indicated that a class of cellular genes known as early response genes are important in the control of cellular growth properties. Two of these genes, c-jun and c-fos, play an important role in the control of cellular differentiation. Because the acute myelogenous leukemia cell line, HL-60, is capable of differentiating to either macrophages or granulocytes, it provides a good model to understand differential gene expression. To determine if the modulation of c-jun was important in the differentiation of HL-60 cells to either macrophages or granulocytes, expression of c-jun mRNA was determined by Northern analysis at various times following treatment with a variety of differentiating agents, including 12- tetradeconyl-phorbol 13-acetate (TPA), retinoic acid (RA), dimethyl sulfoxide (DMSO), or 1,25 dihydroxyvitamin D3 [1,25 (OH)2 D3]. Both TPA and 1,25(OH)2D3, which induce HL-60 cells to differentiate to macrophages, resulted in marked increases in c-jun mRNA; while RA and DMSO, which induce HL-60 cells to differentiate to granulocytes, did not greatly alter c-jun mRNA expression. HL-60 cell lines resistant to macrophage differentiation after exposure to either 1,25(OH)2D3 or TPA did not result in increases in c-jun mRNA. These results suggest that elevation of c-jun mRNA in HL-60 cells correlated temporally with differentiation to macrophages. Thus, c-jun may be a critical cellular transcription factor involved in macrophage differentiation.

scholarly journals Downregulation of vaccinia virus intermediate and late promoters by host transcription factor YY1

2009 ◽  
Vol 90 (7) ◽  
pp. 1592-1599 ◽  
Author(s):  
Bruce A. Knutson ◽  
Jaewook Oh ◽  
Steven S. Broyles
Keyword(s):  
Transcription Factor ◽  
Vaccinia Virus ◽  
Transcriptional Repression ◽  
Late Gene ◽  
Viral Promoter ◽  
Cellular Transcription Factor ◽  
Transcriptional Promoters ◽  
Transcription Factor Yy1 ◽  
Cellular Transcription

Approximately half of the intermediate and late gene transcriptional promoters of vaccinia virus have a binding site for the cellular transcription factor YY1 that overlaps the initiator elements. Depletion of YY1 using RNA interference enhanced the activity of these promoters, while overexpression of YY1 repressed their activity. Viral promoter nucleotide replacements that specifically impair the binding of YY1 mostly alleviated the transcriptional repression and correlated with the ability of YY1 to stably interact with the initiator DNAs in vitro. The transcriptional repression activity was localized to the C-terminal DNA-binding domain of the protein. These results indicate that YY1 functions to negatively regulate these vaccinia virus promoters by binding to their initiator elements.

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