Name: how transcription activators turn genes on
Uploaded: 2020-11-23T11:47:37.000Z
Duration: 2 min 42 s
Channel: JoVE

Transcription activators are proteins that are responsible for allowing RNA polymerase to initiate transcription. They have two essential domains- one that binds to DNA and another one that activates transcription.
The DNA-binding domains contain one of several characteristic structural motifs, including common motifs like the helix-turn-helix, zinc finger, and leucine zipper structures.&#160;
A helix-turn-helix domain is made up of two alpha helices joined together by an amino-acid chain that represents the turn. One helix is responsible for recognizing the DNA sequence and fits into the major groove. These proteins bind to DNA as dimers.&#160;
A zinc finger contains an alpha helix and a two-strand beta sheet held together by a zinc atom. The helix binds to the major groove with the help of two histidines in its amino acid chain.&#160;
A leucine zipper is made up of two monomers that interact with each other in the shape of a Y that binds to the DNA. The monomers consist of leucine at every seventh position at the C-terminal end which interacts with the leucine on the opposite monomer. The N-terminal of the monomer which is made up of basic motifs binds to the DNA.
The other essential domain in the activator, the transcription activating domain, recruits co-activators, essential proteins that mediate the binding of activators to RNA polymerase. These co-activators promote transcription through several mechanisms, such as histone modification, which results in increased access of the transcriptional machinery to the DNA.&#160;&#160;
Activators can also send signals via their co-activators to activate RNA polymerase and initiate transcription.
In some cases, activators are essential to the elongation of the transcript. Some polymerases pause transcription after a few nucleotides and need the presence of an activator to restart transcription.&#160;&#160;
Transcription of a single gene can be regulated by several different activators. When more than one activator is involved in the regulation of transcription, they can act synergistically to drastically increase the rate of transcription in comparison to that of individual activators.

eukaryotische transcriptie-activatoren

Eukaryotic Transcription Activators

Transcriptieactivatoren zijn eiwitten die de transcriptie van genen van DNA naar RNA bevorderen. In de meeste gevallen bevatten deze eiwitten twee afzonderlijke domeinen: een domein dat zich aan DNA bindt en een domein dat transcriptie activeert; In sommige gevallen is echter één enkel domein verantwoordelijk voor zowel binding als activering van transcriptie, zoals te zien is in de glucocorticoïdereceptor en MyoD.

De bindende domeinen zijn in staat regulerende sequenties op het DNA te herkennen en ermee te interageren. Deze domeinen worden ingedeeld in verschillende families en benoemd op basis van de structurele kenmerken die DNA-herkenning en -binding mogelijk maken. Enkele veel voorkomende typen bindingsdomeinen zijn de leucine-ritssluiting, zinkvinger en helix-turn-helix-motieven. Daarentegen zijn domeinen die verantwoordelijk zijn voor activering van gentranscriptie gewoonlijk korte, eenvoudige sequenties en minder complex dan de bindende domeinen. Ze worden op basis van de aminozuursamenstelling ingedeeld in categorieën, zoals glutaminerijk, prolinerijk en alaninerijk.

Transcriptieactivatoren helpen bij de rekrutering van verschillende eiwitten die nodig zijn voor transcriptie, zoals algemene transcriptiefactoren, RNA-polymerase en co-activatoren. Al deze eiwitten samen staan bekend als het pre-initiatiecomplex en zijn afhankelijk van transcriptie-activatoren voor hun rekrutering naar de juiste locatie. Deze activatoren kunnen zich binden aan een plaats dicht bij de promotor van het gen of enkele duizenden basenparen verwijderd van het gen om hun functie uit te voeren. In gevallen waarin ze gebonden zijn aan een plaats weg van het gen, vertrouwen ze op de flexibiliteit van het DNA om te buigen en ze in de nabijheid van de genpromotor te brengen. Transcriptieactivatoren zijn ook nodig om de verlenging van een transcript voort te zetten of de transcriptie opnieuw te starten in gevallen waarin het proces halverwege stopt. Het is bekend dat transcriptie-activatoren synergetisch werken. De transcriptie die wordt bereikt door de werking van meerdere activatoren is hoger dan wat zou gebeuren als een som van individuele factoren die afzonderlijk werken.

Net als andere eiwitten zijn transcriptie-activatoren onderhevig aan post-transcriptionele modificaties. In veel gevallen helpen deze modificaties bij de positieve regulatie van transcriptie. Acetylatie van p53, een activator die genen reguleert die verantwoordelijk zijn voor tumoronderdrukking, vergroot bijvoorbeeld het vermogen ervan om aan DNA te binden.

Eukaryotische transcriptie-activatoren

Transcription activators are proteins that promote the transcription of genes from DNA to RNA. In most cases, these proteins contain two separate domains ...

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JoVE Core

Molecular Biology

Moleculaire biologie

Unit 1

Gene Expression

Genexpressie

KEY TERMS AND CONCEPTS

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how transcription activators turn genes on

Transcription activators are proteins that help turn genes on by promoting transcription from DNA to RNA. They often have two parts. One part binds to DNA, and the other part activates transcription. In some proteins, such as the glucocorticoid receptor and MyoD, one domain can do both jobs.

The DNA-binding part recognizes specific regulatory sequences on the DNA. These binding domains are grouped into families based on their structure. Common examples include the leucine zipper, zinc finger, and helix-turn-helix motifs. The activation part is usually shorter and simpler. It is often described by amino acid content, such as glutamine-rich, proline-rich, or alanine-rich sequences.

Transcription activators also help recruit the proteins needed to start transcription. These include general transcription factors, RNA polymerase, and co-activators. Together, these proteins form the pre-initiation complex. Activators can bind near a gene promoter or thousands of base pairs away. When they bind far away, DNA bending helps bring them close to the promoter.

These proteins can also help transcription continue if it pauses partway through or needs to start again. Many activators work synergistically, which means several together can produce more transcription than each one alone. Like other proteins, activators can be modified after they are made. For example, acetylation of p53 increases its ability to bind DNA and helps regulate genes involved in tumor suppression.

How Transcription Activators Turn Genes On

how-transcription-activators-turn-genes-on

cell specific gene expression

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regulation of expression occurs at multiple steps

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Cells control gene expression at several points between DNA and protein. The most common control point is transcription. At this stage, proteins bind to short regulatory DNA sequences and can either increase or reduce transcription of the linked gene. After transcription, a precursor mRNA is made. This pre-mRNA contains exons, which code for protein, and introns, which do not. It must be processed before translation, and splicing removes the introns and joins the exons. Cells can also regulate...

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prokaryotic transcriptional activators and repressors

prokaryotic-transcriptional-activators-and-repressors

Operon Control by Activators and Repressors

Operon control in prokaryotes depends on activators and repressors. Prokaryotic genes are often arranged in groups, not one by one like in eukaryotes. Genes that help carry out the same biochemical process are placed together with their regulatory elements. This group is called an operon, and it is transcribed into a single polycistronic mRNA strand. Activators and repressors are DNA-binding proteins that control transcription in an operon. Activators bind near the promoter, which is the site...

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The eukaryotic promoter region is a stretch of DNA located upstream of a gene. It includes an RNA polymerase binding site, a transcription start site, and several cis-regulatory sequences. These DNA signals help control when transcription begins. The promoter can be divided into proximal and distal regions. The proximal promoter lies close to the gene and includes cis-regulatory sequences and the core promoter. The core promoter is the RNA polymerase binding site, and it is usually found...

co-activators and co-repressors

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Chromatin control plays a major role in gene transcription in eukaryotes. Gene expression is regulated by several proteins that work together at a gene regulatory site. Some of these proteins bind directly to specific DNA sequences, while co-regulators attach to those regulators but do not bind DNA on their own. Co-regulators can act as co-activators or co-repressors, depending on the complex they join. One co-regulator may even switch roles in different settings. For example, the...

eukaryotic transcription activators

Transcription activators are proteins that help turn genes on by promoting transcription from DNA to RNA. They often have two parts. One part binds to DNA, and the other part activates transcription. In some proteins, such as the glucocorticoid receptor and MyoD, one domain can do both jobs. The DNA-binding part recognizes specific regulatory sequences on the DNA. These binding domains are grouped into families based on their structure. Common examples include the leucine zipper, zinc finger,...

eukaryotic transcription inhibitors

How Eukaryotic Gene Repressors Work

Eukaryotic gene repressors help turn specific genes off when the cell needs to control growth, development, or other biochemical processes. These DNA-binding proteins regulate gene expression in eukaryotes. Their presence at the right time and place can be triggered by hormones and signals from other cells. Most transcription inhibitors have two main parts. One part binds DNA, and the other is a repressor domain, which helps shut down transcription. Repressor domains can connect with basal...

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DNA Methylation and Histone Changes

Epigenetic regulation controls gene activity without changing the DNA sequence. It helps determine when genes are turned on or off in a cell. Two major epigenetic mechanisms are DNA methylation and histone modification. DNA methylation adds chemical groups to DNA, while histone changes affect how tightly DNA is packed around histone proteins. These changes can make genes easier or harder to use. In high school biology, epigenetic regulation is important for understanding how cells with the...

genomic imprinting and inheritance

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key terms and concepts

Learn how transcription activators bind DNA, recruit the pre-initiation complex, and boost gene transcription with examples like p53, MyoD, and the glucocorticoid receptor.

How Transcription Activators Turn Genes On | JoVE K12

molecular biology

JoVE Core Molecular Biology showcases the molecular processes of the cell through clear and concise animated video lessons. Additionally, in scientist-in-action videos, these concepts' application is demonstrated through real experiments in modern laboratories.

How Transcription Activators Turn Genes On

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