Transcriptional activators are proteins that bind to DNA and stimulate transcription of nearby genes. Most activators enhance RNA polymerase
RNA polymerase
RNA polymerase, abbreviated RNAP or RNApol, officially DNA-directed RNA polymerase, is an enzyme that synthesizes RNA from a DNA template. RNAP locally opens the double-stranded DNA so that one strand of the exposed nucleotides can be used as a template for the synthesis of R…
How do activators and repressors affect transcription?
Transcription factors that are activators boost a gene's transcription. Repressors decrease transcription. Repressors decrease transcription. Groups of transcription factor binding sites called enhancers and silencers can turn a gene on/off in specific parts of the body.
What are repressors and activators?
These mechanisms can be generally grouped into three main areas:
- Control over polymerase access to the gene. This is perhaps the broadest of the three control mechanisms. ...
- Productive elongation of the RNA transcript. Once polymerase is bound to a promoter, it requires another set of factors to allow it to escape the promoter complex and begin successfully ...
- Termination of the polymerase. ...
Does prokaryotic transcription have activators?
Transcription of prokaryotic genes in an operon is regulated by two types of DNA binding proteins known as activators and repressors. Activators bind to the promoter, the site of transcription initiation, and aid in the binding of RNA polymerase, the key enzyme involved in transcription.
What is an activator and repressor?
is that activator is one who, or that which, activates while repressor is anything that represses. Other Comparisons: What's the difference? One who, or that which, activates. (biology) Any chemical or agent which regulates one or more genes by increasing the rate of transcription.
What is an activator and repressor?
A regulator protein that turns genes ON when it binds DNA is called an “activator protein,” and a regulator protein that turns genes OFF when it binds DNA is a “repressor protein.”
How do activators affect transcription?
Transcription factors that are activators boost a gene's transcription. Repressors decrease transcription. Groups of transcription factor binding sites called enhancers and silencers can turn a gene on/off in specific parts of the body.
Is an activator a promoter?
An activator facilitates the upregulation of the transcription process by binding to enhancers, while promoter is the site at which RNA polymerase binds, and transcription initiation takes place, and repressor downregulates transcription by binding to silencers.
What is an activator in biology?
Definitions of activator. (biology) any agency bringing about activation; a molecule that increases the activity of an enzyme or a protein that increases the production of a gene product in DNA transcription.
What is the role of an activator quizlet?
The main function of activators and co-activators is to attract position, and modify GTFs and RNA Pol 2 at core promoter. They accomplish this by: acting directly on the transcription initiation machinery, DNA bending (architectural proteins) - allows activators to function at a distance through DNA looping.
What is an example of an activator?
An example of an enzyme activator is heparin, which enhances the activity of antithrombin III, a protease that regulates the activity of the coagulation pathway.
Is an enhancer and an activator the same thing?
An enhancer is a DNA sequence that promotes transcription. Each enhancer is made up of short DNA sequences called distal control elements. Activators bound to the distal control elements interact with mediator proteins and transcription factors.
What are activators and enhancers?
enhancer: a short region of DNA that can increase transcription of genes. repressor: any protein that binds to DNA and thus regulates the expression of genes by decreasing the rate of transcription. activator: any chemical or agent which regulates one or more genes by increasing the rate of transcription.
Which subfamily is transcriptional activator?
The NR5 subfamily are transcriptional activators dependent on the AF-2 domain and having no clear AF-1 function in the A/B domain41,80,82. Nevertheless, an activation function, called AF-1 or AF-3, has been mapped in the hinge region of SF-1 both in mammals and zebrafish 80,85.
What are the key transcriptional activators of IL-1?
Members of the IRF family can also activate IL-1β. Three key transcriptional activators, PU.1, C/EBP, and IRF4 , are capable of rapidly inducing IL-1β during stimulation of monocytes (Zhang et al., 2008 ). Autophagic dying MCF-7 cells upregulate expression of IRF4, and this upregulation is strongly present during their engulfment by non-professional (living MCF-7) and professional (macrophage) phagocytes ( Figure 14.3 ). IRF8, another member of the IRF family, which is a key factor required for macrophage development, makes these cells responsive to IFN-γ-LPS signaling, thereby triggering expression of genes important for innate immunity. IRF8 interacts with partner proteins PU.1 and IRF1, allowing it to bind to the IFN-stimulated response element ( Laricchia-Robbio et al., 2005 ). The autophagic dying MCF-7 and not the anoikic-autophagic ones could induce the expression of IRF1 and IRF8 in macrophages engulfing them. On the contrary, the engulfment of anoikic-autophagic MCF-7 cells induced no change in the IRF1 and decreased the expression of IRF8 in the macrophages. Living MCF-7 cells engulfing autophagic or anoikic-autophagic MCF-7 cells seem not to be armed with the same IRF machinery that professional phagocytes have. Clearly, death through autophagy can differentially activate IL-1β activating transcription activators such as IRFs 1, 4 and 8 in macrophages ( Figure 14.3 ).
What are the targets of Ca2+-activated signaling pathways?
Once Ca 2+-activated signaling pathways converge on the nucleus, they target transcriptional activators that can initiate gene expression. One major nuclear target of activity-dependent signaling pathways is the transcription factor CREB, which initiates transcription of genes containing sites of Ca2+ /cAMP response elements (CREs) within their promoter ( Brindle and Montminy, 1992; Sassone-Corsi, 1995 ). CREB contains a 61-amino acid stretch known as the kinase-inducible domain (KID) that is rich in potential serine and threonine phosphorylation sites ( Gonzalez et al., 1989, 1991 ). Within the KID, phosphorylation at serine-133 is correlated with activity-regulated gene expression ( Ginty et al., 1993; Jeon et al., 1997; Ji and Rupp, 1997; Lee et al., 1999; Sakaguchi et al., 1999 ). Mutation of this residue to a non-phosphorylatable alanine abolishes Ca 2+ -mediated, CREB-dependent transcription ( Sheng et al., 1991 ). Multiple signaling pathways converge on CREB to induce gene expression by Ser-133 phosphorylation. These include the Ca 2+ -calmodulin-activated kinases CaMKIV and PKA, as well as the Ras-dependent RSKs ( Deisseroth et al., 1998; Hagiwara et al., 1993; Sheng et al., 1991; West et al., 2001 ). Ser-133 phosphorylation alone is insufficient to activate CREB-mediated transcription. Ser-133-phosphorylated CREB acts together with a co-adaptor, the CREB-binding protein (CBP) ( Chrivia et al., 1993 ), which itself needs to be phosphorylated by CaMKIV in order to recruit the RNA polymerase II transcription complex ( Impey et al., 2002 ). CBP also has intrinsic histone acetylase activity, which aids in opening chromatin, rendering the DNA more accessible for transcription ( Zocchi and Sassone-Corsi, 2010 ). Phosphorylation of Ser-142 on CREB by CaMKII can free it from CBP regulation by sterically hindering binding ( Parker et al., 1998 ). This also inhibits CREB activation by CaMKIV ( Sun et al., 1994 ), but not by PKA ( Kornhauser et al., 2002 ). This differential control likely serves to integrate signaling through multiple activated kinase cascades, ultimately influencing the outcome of CREB-mediated gene expression ( Deisseroth and Tsien, 2002 ).
What is the function of the PlcR gene?
The plcR gene was initially identified in B. thuringiensis as encoding a transcriptional activator of the plcA gene for PI-PLC [392]. The protein product PlcR activates transcription of its own gene and that of plcA, at the end of exponential growth. Genetic screening demonstrated that PlcR is a pleiotropic regulator that controls transcription of several genes encoding exported proteins apparently involved in virulence [63]. They included various degradative enzymes and cytotoxins, as well as the haemolytic and non-haemolytic enterotoxins, HBL and NHE. Alignment of the DNA regions coding for promoters activated by PlcR revealed a highly conserved palindromic sequence (TATGNANNNNANCATA) designated as PlcR box. The –10 boxes of the PlcR-regulated promoters correspond to that recognized by the RNA polymerase associated with the sigma factor σ A. Nevertheless, the –35 regions of such promoters significantly differ from the sequences generally recognized by σ A. The starts of PlcR-regulated transcripts were located at various distances downstream of the palindromic sequence (varied from a few nucleotides up to about 200 nucleotides in the case of the hbl and nhe operons).
What is the GATA3 gene?
GATA binding protein 3 (GATA3) is a transcriptional activator highly expressed by the luminal epithelial cells in the breast. It is involved in growth and differentiation. Gene expression profiling has shown that GATA-3 is highly expressed in the luminal A subtype of breast cancer.140,384 In an immunohistochemical study of 139 breast cancers, Mehra and coworkers showed that low GATA3 expression was associated with higher histologic grade (P < 0.001), positive nodes (P = 0.002), larger tumor size (P = 0.03), negative ER and PR (P < 0.001 for both), and HER2/neu overexpression (P = 0.03). 428 Patients whose tumors expressed low GATA3 had significantly shorter overall and disease-free survival when compared with those whose tumors had high GATA3 levels. 428 In a much larger series of 3119 breast cancer cases, Voduc and associates showed somewhat similar findings; however, they also clarified some of the issues. 429 In their study, GATA-3 was almost exclusively expressed in ER-positive patients and was also associated with lower tumor grade, older age at diagnosis, and the absence of HER2 overexpression. GATA-3 was a marker of good prognosis and predicted for superior breast cancer-specific survival, relapse-free survival, and overall survival in univariate analysis. 429 However, in multivariate models including patient age, tumor size, histologic grade, nodal status, ER status, and HER2 status, GATA-3 was not independently prognostic for these same outcomes. Furthermore, in the subgroups of ER-positive patients treated with or without tamoxifen, GATA-3 was again nonprognostic for all outcomes. 429
Is YY1 a transcriptional activator?
The dual function of YY1 as a transcriptional activator and repressor has been suggested to depend on the nature of binding sites, chromatin configuration, interaction with coactivators or corepressors, or even competition with other transcription factors for binding sites. Among these factors, interactions with cofactors able to modulate the transcriptional outcome mediated by YY1 appear critical.
What is the interaction between transcriptional activators and promoters?
The interaction of enhancer-bound transcriptional activators and promoter-bound transcription factors is mediated by coactivators. Coactivators are proteins that do not bind DNA themselves but interact with DNA-bound transcriptional activator proteins, thereby facilitating protein–protein interaction.
What is the transcriptional activator of AAF?
A transcriptional activator known as ‘AggR’, encoded by pAAs, is the major EAEC virulence regulator controlling diverse virulence genes encoded by pAAs (including biogenesis of AAF) as well as by chromosomes.
What is the function of the yeast transcriptional activator Gal4?
The yeast transcriptional activator Gal4 binds a specific DNA sequence called UAS (upstream activating sequence) and activates transcription of a gene placed downstream of the UAS. We constructed a gene trap construct (T2KSAGFF) that contains a splice acceptor and the gal4ff gene and an enhancer trap construct (T2KhspGFF) that contains the zebrafish hsp70 promoter and the gal4ff gene ( Fig. 6A) ( Asakawa et al., 2008 ). Gal4FF is a modified version of the yeast transcription activator Gal4, which has the Gal4 DNA-binding domain fused to two short transcription activator segments from the herpes simplex viral protein VP16 ( Baron et al., 1997). Plasmids carrying these constructs are injected with the transposase mRNA into fertilized eggs. By crossing the injected fish with the UAS:GFP reporter fish, Gal4FF transgene insertion and expression are identified as GFP expression in the offspring (Fig. 6B). Thus, a large number of transgenic fish expressing Gal4FF in specific cells, tissues, and organs have been created (Fig. 6C ).
How can genes be inactivated?
As described previously, genes can be inactivated by deletions or insertions created during repair of a DSB by nonhomologous end joining. Where this is the intention, mRNA encoding a sequence-specific endonuclease can be injected into the cytoplasm of a zygote. This will be translated to the endonuclease protein that, if provided with a nuclear localization signal, will be transported into the nucleus of the developing embryo. Where more sophisticated modifications are required, such as targeted sequence replacement, this is best achieved by homologous recombination with a gene targeting vector. This requires two steps, injection of endonuclease mRNA into the cytoplasm, and injection of the gene targeting vector DNA into a pronucleus. Gene targeting vectors used in this system are often termed “donor vectors.”
How many genes can an enhancer regulate?
An enhancer can regulate more than one gene in a position- and orientation-independent manner. The mechanism of enhancer action is thought to involve looping of the DNA, thereby bringing the enhancer-bound transcriptional activators close to the promoter-bound transcription factors.
How do enhancers affect transcription?
Enhancers bind specific transcriptional activators and enhance the rate of transcription. Enhancers can be located close to the transcription start site, upstream or downstream from the transcription start site, and even within introns. An enhancer can regulate more than one gene in a position- and orientation-independent manner. The mechanism of enhancer action is thought to involve looping of the DNA, thereby bringing the enhancer-bound transcriptional activators close to the promoter-bound transcription factors. In doing so, enhancers increase the concentration of activators near the promoter, which directly or indirectly interact with the promoter to initiate transcription. The interaction of enhancer-bound transcriptional activators and promoter-bound transcription factors is mediated by coactivators. Coactivators are proteins that do not bind DNA themselves but interact with DNA-bound transcriptional activator proteins, thereby facilitating protein–protein interaction. Some examples of coactivator proteins are CBP/p300, p160, p300/CBP-interacting protein (p/CIP), p300/CBP-associated factor (p/CAF), yeast transcriptional adaptor GCN5, steroid receptor coactivator-1 (SRC-1), and there are many others. The opposite of enhancers are silencers, which bind transcriptional suppressor proteins and suppress transcription, thereby acting as negative regulatory elements. Like enhancers, silencers can also function in an orientation-, position-, and distance-independent manner, and they can also be located within introns.
Which proteins are only expressed in cells that have exited the cell cycle?
Runx-2 is only expressed in cells in which proliferation has been arrested. p-107 and p-130 are both expressed in cells that have exited the cell cycle. The retinoblastoma (pRB) family proteins p-107 and p-130 regulate the cell cycle by regulating cyclin-dependent kinases and cyclins.
What is the mechanism of action of transcription factors?
The mechanism of action of transcription factors is to promote or prevent the binding of RNA polymerase to the promoter sequence of the gene. RNA polymerase is the enzyme responsible for the synthesis of a mRNA molecule by transcribing the coding region of a gene. Activators facilitate the binding of RNA polymerase to the promoter ...
Which transcription factor binds to the promoter?
RNA polymerase itself binds to the promoter region in prokaryotes while transcription factors aid the binding of RNA polymerase to the promoter in eukaryotes. This type of transcription factor is known as basal (general) transcription factors.
What are the transcription factors that bind to enhancer regions?
Activators are the transcription factors that bind to the enhancer regions, activating the transcription by facilitating the binding of RNA polymerase and/or basal transcription factors to the promoter. The action of activators is shown in figure 1.
What are transcription binding sites?
Transcription binding sites are known either as enhancers or silencers based on the effect of the bound transcription factor on transcription. Enhancers turn the genes “on” upon binding of transcription factors while silencers turn the genes “off” upon binding transcription factors. Activators are the transcription factors ...
What are repressors and activators?
What are Activators and Repressors. Activators and repressors are two types of transcription factors that regulate the gene expression at the transcriptional level. Transcription factors are trans-acting regulatory proteins, determining the time, location, and the efficiency of transcription. The mechanism of action of transcription factors is ...
What are the two types of transcription factors involved in the regulation of gene expression at the transcription level?
Activators and repressors are the two types of transcription factors involved in the regulation of gene expression at the transcription level. Activators bind to the enhancer regions in the DNA and facilitate the binding of RNA polymerase to the promoter.
What is the role of transcription factors in gene expression?
Transcription factors are the proteins responsible for the regulation of gene expression at the transcriptional level. They bind to the transcription control elements in DNA. Depending on the function, ...
