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

转录 激活剂是蛋白质 负责 允许RNA聚合酶 启动转录。它们有两个 必不可少的领域，一个 与DNA结合 还有一个 激活转录。DNA结合域包含 几个特征之一 结构图案 包括常见的主题，像螺旋-转-螺旋 锌指 和亮氨酸拉链结构。螺旋-转-螺旋 域组成 两个阿尔法螺旋 联结在一起 通过氨基酸链 代表转弯。一个螺旋负责 识别DNA序列 并适合大槽。这些蛋白质结合 以DNA为二聚体。锌指含有 一个阿尔法螺旋 以及两链的贝塔版表，通过锌原子结合在一起。螺旋线绑定到 大槽 在两个组氨酸的帮助下 及其氨基酸链。制成亮氨酸拉链 由两种单体组成 互相交流 呈Y形 结合到DNA上。单体由亮氨酸组成 在第七个位置 在C端 结束，它相互作用 亮氨酸 相反的单体。N端 单体 由基本组成 基序，与DNA结合。其它必不可少的 激活子中的域，转录 激活域，招募共同激活子，必需蛋白 介导激活剂 与RNA聚合酶的结合。这些共激活剂 促进转录 通过几种机制，例如 作为组蛋白修饰，导致访问增加 转录机制 脱氧核糖核酸。激活器也可以发送 通过其辅助激活器发出信号 激活RNA聚合酶 并开始转录。在某些情况下，激活剂是 伸长率必不可少的 转录本。一些聚合酶 暂停转录 几个核苷酸后需要 活化剂的存在 重新开始转录。转录 一个基因可以 受几个 不同的激活剂。当不止一个 涉及激活剂 在规定中 转录 它们可以协同行动 以急剧增加 转录率 形成对比于 个体激活剂。

<ol>
	<li>马，J.（2006 年）。转录激活剂和激活机制。在基因表达和调节中（第 147-158 页）。斯普林格，纽约州纽约市。</li>
	<li>格林，MR（2005 年）。真核生物转录激活:正好在目标上。分子细胞，18（4），399-402。</li>
</ol>

真核转录激活剂

Eukaryotic Transcription Activators

转录激活剂是促进基因从 DNA 转录为 RNA 的蛋白。 在大多数情况下，这些蛋白包含两个独立的结构域——一个与 DNA 结合的结构域和一个用于激活转录的结构域； 然而，在某些情况下，单个结构域负责转录的结合和激活，如糖皮质激素受体和 MyoD 中所见。

结合域能够识别 DNA 上的调控元件并与之相互作用。 这些结构域被分为不同的家族，并根据能够识别和结合 DNA 的结构特征来命名。 一些常见类型的结合结构域包括亮氨酸拉链、锌指和螺旋-转角-螺旋基序。 相反，负责基因转录激活的结构域通常是短而简单的序列，并且不如结合结构域复杂。 它们根据氨基酸组成分为富含谷氨酰胺、富含脯氨酸和富含丙氨酸等类别。

转录激活剂有助于招募转录所需的各种蛋白，例如通用转录因子、RNA 聚合酶和共激活因子。 所有这些蛋白一起被称为预起始复合物，并依赖于转录激活因子将其募集到适当的位置。 这些激活剂可以结合到靠近基因启动子的位点或远离基因几千个碱基对的位点以发挥其功能。 当它们结合到远离基因的位点时，它们依靠 DNA 的灵活性来弯曲并使它们靠近基因启动子。 当过程中途停止时，还需要转录激活因子来继续转录物的延伸或重新启动转录。 已知转录激活因子具有协同作用。 通过多个激活因子的作用实现的转录高于单独作用的单个因素的总和。

与其他蛋白一样，转录激活剂也会发生转录后修饰。 在许多情况下，这些修饰有助于转录的正向调节。 例如，p53（一种调节负责肿瘤抑制的基因的激活剂）的乙酰化会增加其与 DNA 结合的能力。

转录激活因子是促进基因从DNA转录为RNA的蛋白质。在大多数情况下，这些蛋白质包含两个独立的结构域……

Education

教育

JoVE Core

Molecular Biology

分子生物学

Unit 1

第一单元

Gene Expression

基因表达

KEY TERMS AND CONCEPTS

关键术语与概念

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

How Cells Switch Genes On and Off

Cells switch genes on and off to make different proteins for different jobs. In multicellular organisms, many cell types are built from the same DNA, but they do not use the same genes in the same way. This difference in gene expression helps explain why cells can look and act so differently. Liver cells are a clear example. They help detoxify blood, make bile to help digest fats, and produce proteins needed for metabolism. To do these jobs, liver cells must express a specific set of genes.

regulation of expression occurs at multiple steps

regulation-of-expression-occurs-at-multiple-steps

How Cells Control Gene Expression

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...

cis-regulatory sequences

How Cis-Regulatory DNA Controls Transcription

Cis-regulatory sequences are short, non-coding DNA segments that control gene transcription. They sit on the same chromosome as the genes they regulate and act as binding sites for transcriptional regulators. In eukaryotes, these proteins help control gene expression patterns in different cell types. These DNA sequences can be close to a gene or thousands of bases away. When they are far from the gene in the DNA sequence, they are often brought close together in space because chromosomes are...

cooperative binding of transcription regulators

cooperative-binding-of-transcription-regulators

How Transcription Factors Bind DNA

Transcriptional regulators bind to cis-regulatory DNA sequences to control gene transcription. These DNA sequences are very short, usually fewer than ten nucleotide pairs long. Because they are so short, the same sequence can appear by chance in many places across the genome. Some regulators can also bind to groups of similar sequences. That raises the chance of random binding even more. To lower this risk, transcription regulators often form dimers, which are pairs of proteins that bind a DNA...

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...

operons

Operons in Bacterial Gene Control

Operons help bacteria control groups of genes at the same time. An operon is a set of genes that are regulated together and can be turned on or off as a unit. This shared control helps bacteria respond quickly to changes in their environment. In many operons, a promoter gives RNA polymerase a place to bind and start transcription. The operon also includes a regulatory region that helps control whether the genes are expressed. When conditions change, the cell can use this setup to manage gene...

the eukaryotic promoter region

Eukaryotic Promoter Motifs and Gene Control

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

Chromatin Control in Gene Transcription

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...

combinatorial gene control

Gene Expression by Transcription Factor Combinations

Gene expression can depend on combinations of transcription factors working together. In combinatorial gene control, several transcription factors act in a coordinated way to regulate a single gene. If one or more of these factors are missing, the level of gene expression or repression can change a lot. This kind of control helps explain how a relatively small number of transcription factors can regulate a very large number of genes. More than 30,000 genes are controlled by about 2,000 to...

induced pluripotent stem cells

Reprogramming Cells into Stem Cells

Induced pluripotent stem cells are created by reprogramming mature cells back into a stem-cell state. This process shows that specialized cells can be changed into cells with broader developmental potential. The topic is important in biology because it links cell identity, gene control, and stem cell research. These cells begin as ordinary body cells and are pushed to de-differentiate, or lose their specialized features. After reprogramming, they behave like pluripotent stem cells, which means...

master transcription regulators

MEF2C and Gene Control Cascades

MEF2C is a master transcription regulator that controls gene expression in coordinated cascades. These regulators are proteins that manage the activity of multiple genes that often work together to produce a complex outcome. When a master transcription regulator is activated, it can start a chain of transcriptional activation that supports that outcome. Master transcription regulators can act in two main ways. They may bind directly to the regulatory sequences of several genes involved in a...

epigenetic regulation

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

Genomic Imprinting in Human Disease

Genomic imprinting affects how some inherited genes are turned on or off in human cells. Diploid organisms inherit chromosomes from both parents, and each gene usually has two alleles. In most cases, both alleles are expressed. If one allele is missing or mutated, the other can often compensate, but some genes do not work that way. In genomic imprinting, a gene or its regulatory sequence carries chemical tags, such as methyl groups, on the copy inherited from only one parent. These tags are...

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 分子生物学通过清晰简洁的动画视频课程展示了细胞的分子过程。此外，在科学家在行动的视频中，这些概念的应用是通过现代实验室中的真实实验演示的。

How Transcription Activators Turn Genes On

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