Name: how cis-regulatory dna controls transcription
Uploaded: 2020-11-23T11:47:37.000Z
Duration: 2 min 2 s
Channel: JoVE

منظمات النسخ هي بروتينات ترتبط ب امتدادات صغيرة محددة من دى إن أيه غير المشفر،المعروفة باسم تسلسلات سيز-المنظمة هذه المكونات الأساسية لتنظيم الجينات موجودة في جميع أنحاء الجينوم. منظمات النسخ يمكنها الارتباط بالتسلسلات التنظيمية لسيز على ال دى إن أيه فى شكله الحلزونى المزدوج. الشكل الحلزونى الخاص ب دى إن أيه له إثنان من التجاويف التي تختلف في الحجم.الإخدود الأوسع معروف بالأخدود الرئيسي يكون قابلية الوصول إليه أكثر من الأصغر،الإخدود الصغير مما أدى إلى أن معظم التفاعلات تحدث في الأخدود الرئيسي حواف القواعد النيتروجينية مكشوفة على طول الأخاديد وتكون قادرة على الترابط الهيدروجيني وغيرها من التفاعلات الغير التساهمية. هذا الربط الخاص بمنظمات النسخ هو تخصصى التسلسل. ولكن،التسلسلات ذات الصلة الوثيقة تكون أيضا مُعَرَفة.هذا الارتباط يكون ثابت للغاية بسبب إشتراك التفاعلات الغير تساهمية المتعددة. التسلسلات التنظيمية سيز يمكن أن تحكم كل جانب فى نسخ الجينات،بما في ذلك تثبيط أو بدء النسخ،وكذلك معدل النسخ. يمكن أن يكونوا مصنفين على نطاق واسع إلى تلك التي هي على مقربة من موقع النسخ وأولئك الذين هم على بعد الآلاف من أزواج القاعدة.تلك التي هي عادة ما تكون قريبة تكون جزء من تسلسل المحفز الذى يبدء نسخ الجينات. الذين هم على بعد يمكنهم المشاركة في أي من التعزيز أو إسكات النسخ. في كثير من الأحيان،التعبئة المدمجة من دى إن أيه والكروموسوم تتسبب في أن تكون هذه التسلسلات مكانيًا قريبًة من الجين الذي ينظمونه،حتى لو كانوا بعيدون في التسلسل.مزيج من عدة تسلسلات تنظيمية سيز تتحكم في تعبير معظم الجينات. نادراًماسيكون الجين تحت سيطرة تسلسل واحد فقط.

<ol>
	<li>ألبرتس وآخرون ، الطبعة السادسة ؛ الصفحات 373-375</li>
	<li>باكالي، م. (2011). التطور الجزئي للعناصر التنظيمية لرابطة الدول المستقلة: مثال من جين تجزئة القاعدة الزوجية fushi tarazu في ذبابة الفاكهة السوداء المجموعة الفرعية. PloS واحد ، 6 (11).</li>
</ol>

التسلسلات التنظيمية المتزامنة cis

Cis-regulatory Sequences

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التسلسلات التنظيمية Cis هي أجزاء قصيرة من الحمض النووي غير المشفر والتي توجد على نفس الكروموسومات مثل الجينات التي تنظمها. تعمل هذه الأجزاء كمواقع الربط لمنظمات النسخ، وهي البروتينات المسؤولة عن التحكم في نسخ الجينات والتعبير الجيني التفاضلي عبر أنواع الخلايا في حقيقيات النوى. يمكن أن تكون التسلسلات التنظيمية المتزامنة Cis قريبة من الجين محل الاهتمام أو بعيدة بآلاف القواعد في تسلسل الحمض النووي؛ ومع ذلك، فإن تلك التسلسلات البعيدة غالبًا ما تكون موجودة مكانيًا بالقرب من الجين الذي تنظمه بسبب التغليف المحكم للحمض النووي في الكروموسوم. تنظم الخلايا القريبة في التسلسل بدء نسخ الجينات، بينما تعمل تلك البعيدة على تعزيز أو إسكات عملية نسخ الجينات. إن تأثيرات العديد من التسلسلات التنظيمية المتزامنة Cis تنظم معظم الجينات بشكل نسبي. ومع ذلك، في بعض الأحيان، ينظم تسلسل تنظيمي واحد من Cis نسخ الجين.

ترتبط عوامل النسخ بالتسلسلات التنظيمية المتزامنة Cis عندما يكون الحمض النووي في شكله الحلزوني المزدوج. تالربط منظمات النسخ تسلسلات محددة ولكنها قادرة على الربط تسلسلات وثيقة الصلة أيضًا. يحتوي الحلزون المزدوج على نوعين من الأخدود: الأخدود الأصغر حجمًا والأخدود الأكبر حجمًا. من المرجح أن ترتبط العوامل التنظيمية بأخاديد الحمض النووي الرئيسية بسبب حجمها. تتعرف منظمات النسخ على تسلسلات تنظيمية محددة من Cis من خلال السمات الكيميائية المميزة الموجودة عند حواف أزواج القواعد النيتروجينية. على سبيل المثال، تحتوي القواعد على مانحين ومستقبلات مختلفة لرابطة الهيدروجين مكشوفة على طول الأخدود والتي يمكن أن تشكل روابط هيدروجينية مع منظمات النسخ. نظرًا لأن العديد من التفاعلات غير التساهمية تشارك أيضًا في هذا الارتباط، فإن الارتباط مستقر للغاية.

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التسلسلات التنظيمية المتزامنة Cis

التسلسلات التنظيمية لرابطة الدول المستقلة هي أجزاء قصيرة من الحمض النووي غير المشفر الموجودة على نفس الكروموسومات مثل الجينات التي تنظمها. هذه الشظايا ...

Education

JoVE Core

Molecular Biology

البيولوجيا الجزيئية

Unit 1

الوحدة الأولى

Gene Expression

التعبير الجيني

KEY TERMS AND CONCEPTS

المصطلحات والمفاهيم الأساسية

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 tightly packed. Sequences near the gene usually help start transcription, while distant sequences can enhance or silence transcription.

Most genes are controlled by several cis-regulatory sequences. In some cases, only one cis-regulatory sequence regulates a gene. Transcription factors bind to these sequences when DNA is in its double-helix form.

Transcriptional regulators bind specific DNA sequences, but they can also bind closely related sequences. They often interact with the major groove of DNA because it is larger than the minor groove. Regulators recognize cis-regulatory sequences by chemical features at the edges of the base pairs, including hydrogen bond donors and acceptors. These interactions, along with other non-covalent forces, make the binding highly stable.

How Cis-Regulatory DNA Controls Transcription

how-cis-regulatory-dna-controls-transcription

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

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

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,...

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 cis-regulatory DNA sequences bind transcription factors, control gene transcription, and help turn genes on or off in different cell types.

How Cis-Regulatory DNA Controls Transcription | 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 Cis-Regulatory DNA Controls Transcription

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