Name: dna damage repair by excision
Uploaded: 2026-08-26T08:19:31.026Z
Duration: 1 min 46 s
Channel: JoVE

K12 Standards

new-jersey-student-learning-standards-for-science

New Jersey Student Learning Standards for Science

High School

Life Science

from-molecules-to-organisms-structures-and-processes

From Molecules to Organisms: Structures and Processes

HS-LS1-1

Nucleotide Excision Repair

- L&#x27;exposition de l&#x27;ADN &#xE0; la lumi&#xE8;re ultravioletteet &#xE0; certains compos&#xE9;s chimiques canc&#xE9;rog&#xE8;nespeut entra&#xEE;ner une l&#xE9;sion volumineuse,une distorsion sp&#xE9;cifique de la structure normale. 
Ce type de d&#xE9;g&#xE2;t peut &#xEA;tre r&#xE9;par&#xE9; par un processusnomm&#xE9; r&#xE9;paration par excision de nucl&#xE9;otides. 
Le processus commence quand un complexe enzymatique,montr&#xE9; ici dans E. 
 Coli,contenant les prot&#xE9;ines UvrA et UvrB,voyage le long de l&#x27;ADNet d&#xE9;tecte les aberrations physiques de la l&#xE9;sion. 
En cet endroit, les brins sont s&#xE9;par&#xE9;s,et les enzymes endonucl&#xE9;ase, comme UvrC,coupent le brin aux deux extr&#xE9;mit&#xE9;s du d&#xE9;g&#xE2;t. 
L&#x27;enzyme ADN h&#xE9;licase enl&#xE8;ve ensuite le morceau coup&#xE9;. 
Un autre enzyme, l&#x27;ADN polym&#xE9;rase,remplit le vide avec de nouveaux nucl&#xE9;otides. 
Pour finir, l&#x27;enzyme DNA ligasescelle les bords entre le nouveau et l&#x27;ancien ADN,terminant la r&#xE9;paration.

Schärer, Orlando D. « Réparation par excision de nucléotides chez les eucaryotes. » Perspectives de Cold Spring Harbor en biologie 5, n° 10 (2013) : a012609. [<a href="https://dx.doi.org/10.1101%2Fcshperspect.a012609">Source</a>]

réparation par excision de nucléotides

<h4>Aper&#xE7;u</h4>
 
 L&#x2019;exposition aux mutag&#xE8;nes peut endommager l&#x2019;ADN et entra&#xEE;ner des l&#xE9;sions encombrantes qui d&#xE9;forment la structure &#xE0; double h&#xE9;lice ou entravent la transcription appropri&#xE9;e. L&#x2019;ADN endommag&#xE9; peut &#xEA;tre d&#xE9;tect&#xE9; et r&#xE9;par&#xE9; au cours d&#x2019;un processus nomm&#xE9; r&#xE9;paration par excision du nucl&#xE9;otide (NER). La NER utilise un ensemble de prot&#xE9;ines sp&#xE9;cialis&#xE9;es qui analysent d&#x2019;abord l&#x2019;ADN pour d&#xE9;tecter une r&#xE9;gion endommag&#xE9;e. Ensuite, les prot&#xE9;ines de NER s&#xE9;parent les brins et excisent la zone endommag&#xE9;e. Enfin, elles coordonnent le remplacement avec de nouveaux nucl&#xE9;otides qui correspondent.
 
 <h4>Distorsion de l&#x2019;ADN et dommages</h4>
 
 Les cellules sont r&#xE9;guli&#xE8;rement expos&#xE9;es aux mutag&#xE8;nes &#x2014; facteurs dans l&#x2019;environnement qui peuvent endommager l&#x2019;ADN et g&#xE9;n&#xE9;rer des mutations. Le rayonnement UV est l&#x2019;un des mutag&#xE8;nes les plus courants et l&#x2019;on estime qu&#x2019;il introduit un nombre important de changements dans l&#x2019;ADN. Il s&#x2019;agit notamment de courbes ou de plis dans la structure qui peuvent bloquer la r&#xE9;plication ou la transcription de l&#x2019;ADN. Si ces erreurs ne sont pas corrig&#xE9;es, les dommages peuvent provoquer des mutations qui peuvent &#xE0; leur tour entra&#xEE;ner un cancer ou une maladie selon les s&#xE9;quences qui sont perturb&#xE9;es.
 
 <h4>L&#x2019;identification et la r&#xE9;paration des r&#xE9;gions endommag&#xE9;es</h4>
 
 La r&#xE9;paration par excision des nucl&#xE9;otides repose sur des complexes prot&#xE9;iques sp&#xE9;cifiques pour reconna&#xEE;tre les r&#xE9;gions endommag&#xE9;es de l&#x2019;ADN et les signaler afin qu&#x2019;elles soient enlev&#xE9;es et r&#xE9;par&#xE9;es. Dans les procaryotes, le m&#xE9;canisme implique trois prot&#xE9;ines : UvrA, UvrB et UvrC. Les deux premi&#xE8;res prot&#xE9;ines agissent ensemble comme un complexe, progressant le long des brins d&#x2019;ADN pour d&#xE9;tecter toutes les aberrations physiques.
 
 Une fois identifi&#xE9;es, les brins &#xE0; l&#x2019;endroit endommag&#xE9; sont s&#xE9;par&#xE9;s, et les enzymes endonucl&#xE9;ases telles que UvrC coupent et excisent la r&#xE9;gion touch&#xE9;e. L&#x2019;ADN polym&#xE9;rase comble l&#x2019;&#xE9;cart avec de nouveaux nucl&#xE9;otides, puis l&#x2019;enzyme ADN ligase scelle les bords entre le nouvel ADN et l&#x2019;ancien.
 
 <h4>Les mutations dans le NER ont de graves cons&#xE9;quences</h4> 
 
 Dans les procaryotes, le complexe NER se compose des trois prot&#xE9;ines Uvr mais, dans les eucaryotes, plus d&#x2019;une douzaine de prot&#xE9;ines fonctionnent pour r&#xE9;guler la r&#xE9;paration de l&#x2019;ADN. Chez l&#x2019;homme, les mutations de la voie NER peuvent causer des maladies telles que le xeroderma pigmentosum (XP), qui est associ&#xE9; &#xE0; une augmentation de 2000 fois de l&#x2019;incidence du cancer de la peau. Les personnes souffrant d&#x2019;XP sont tr&#xE8;s sensibles &#xE0; l&#x2019;exposition aux UV et peuvent d&#xE9;velopper des br&#xFB;lures cutan&#xE9;es graves apr&#xE8;s seulement quelques minutes d&#x2019;exposition &#xE0; la lumi&#xE8;re du soleil. En outre, les patients XP peuvent montrer des signes de vieillissement pr&#xE9;matur&#xE9; et d&#xE9;veloppent souvent des anomalies neurologiques. Sans un m&#xE9;canisme de r&#xE9;paration fonctionnant correctement, les dommages &#xE0; l&#x2019;ADN peuvent s&#x2019;accumuler et mener &#xE0; la mort anormale de cellules ou &#xE0; des tumeurs potentiellement canc&#xE9;reuses.

Réparation par excision de nucléotides

Overview

Exposure to mutagens can damage DNA and result in bulky lesions that distort the double-helix structure or impede proper transcription. Damaged ...

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Education

Enseignement

JoVE Core

Biology

Biologie

Genetics

Génétique

DNA Structure and Function

Structure et fonction de l'ADN

KEY TERMS AND CONCEPTS

TERMES ET CONCEPTS CLÉS

dna damage repair by excision

DNA damage repair by excision protects cells from mutagens that can change DNA. Exposure to environmental mutagens can create bulky lesions that bend the double helix or block transcription. If these changes are not repaired, they can lead to mutations and may contribute to cancer or disease, depending on which DNA sequences are affected.

Nucleotide excision repair, or NER, is the process that detects and removes this kind of damage. Specialized proteins scan the DNA for a damaged region, then separate the strands around it. The damaged section is cut out, and a matching stretch of new nucleotides is added in its place.

UV radiation is one of the most common mutagens and can introduce many DNA changes. These changes can cause kinks in the DNA structure and interfere with replication or transcription. Because of this, cells rely on repair systems to keep damaged DNA from building up.

In prokaryotes, NER uses three main proteins: UvrA, UvrB, and UvrC. UvrA and UvrB work together as a complex and move along the DNA to spot physical damage. After the damaged site is found, the strands are separated, UvrC cuts out the affected section, DNA polymerase fills the gap, and DNA ligase seals the remaining break.

NER is more complex in eukaryotes, where more than a dozen proteins help control DNA repair. In humans, mutations in the NER pathway can cause xeroderma pigmentosum, or XP. This disorder is linked to a 2000-fold increase in skin cancer risk, strong sensitivity to UV light, severe burns after only a few minutes in sunlight, premature aging, and neurological problems. Without a working repair system, DNA damage can accumulate and lead to abnormal cell death or cancerous tumors.

DNA Damage Repair by Excision

the dna helix

How DNA Stores Genetic Information

DNA stores genetic information that is passed from one generation to the next in organisms and most viruses. It is built from two strands of nucleotides that twist together into a double helix. The story of how scientists uncovered this structure developed step by step over nearly a century. Each DNA strand is made of nucleotides. A nucleotide contains the sugar deoxyribose, a phosphate group, and one of four nitrogen bases: adenine (A), guanine (G), cytosine (C), or thymine (T). Adenine and...

dna packaging

Chromatin and Histones in DNA Packing

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organization of genes

Genes, Introns, and Regulatory DNA

Eukaryotic genes are arranged within DNA along with non-coding regions that help control gene activity. A DNA strand includes genes and intergenic regions, which are the stretches between genes. These regions do not code for proteins, but they can contain important regulatory elements such as promoters, enhancers, and silencers. A gene itself is not a single continuous coding block. It usually contains protein-coding exons and non-coding introns. After DNA is transcribed into pre-mRNA in the...

karyotyping

Chromosome Stains for Detecting Disorders

Chromosome staining helps scientists find genetic disorders by showing the number and physical features of chromosomes. These features appear after DNA condenses into chromosomes during mitosis. Cytogeneticists then stop mitosis and stain the chromosomes to study their banding pattern. The pattern reveals details such as chromosome number, shape, and type. A chromosome description like this is called a karyotype. To create one, scientists take an image of the stained chromosomes and identify...

replication in prokaryotes

How Prokaryotic DNA Is Copied

Prokaryotic DNA is copied through a coordinated process with three main stages: initiation, elongation, and termination. It begins when initiator proteins bind to the single origin of replication, or ori, on the cell’s circular chromosome. The DNA then copies around the circle in both directions, starting from two replication forks, and this produces two DNA molecules. Several proteins work together to open and protect the DNA during replication. Topoisomerase cuts one side of the...

replication in eukaryotes

Eukaryotic DNA Copying and Telomeres

Eukaryotic DNA copying is tightly regulated and must duplicate many linear chromosomes before cell division. The process is highly conserved and uses many proteins with specialized roles. It moves through initiation, elongation, and termination, and it ends with two complete sets of chromosomes in the nucleus. Eukaryotic replication shares basic steps with prokaryotic DNA replication, but the larger genome and linear chromosomes require more proteins. Replication begins at multiple origins of...

proofreading

DNA Polymerase Fixes Replication Errors

DNA polymerase helps copy DNA and fix mistakes during replication. It adds nucleotides in a sequence that matches the template DNA strand. The enzyme also has a higher affinity for the correct base, which helps keep DNA replication accurate. As new genomic DNA is made, it is synthesized in the 5’ to 3’ direction. In many cells, DNA polymerases have different jobs in this process. DNA polymerase delta and DNA polymerase epsilon can proofread when nuclear DNA is being copied. These polymerases...

mismatch repair

DNA Mismatch Repair in Replication

DNA mismatch repair fixes copying errors that happen during DNA replication. When DNA polymerase makes a mistake, the cell can detect a wrong base pair, such as A with G or T with C, and replace it with the correct nucleotide. This repair system works in both prokaryotes and eukaryotes and depends on several proteins. The Mutator protein family plays a central role in this process. In bacteria such as Escherichia coli, MutS first binds the mismatch. MutL then helps identify which strand is the...

nucleotide excision repair

DNA damage repair by excision protects cells from mutagens that can change DNA. Exposure to environmental mutagens can create bulky lesions that bend the double helix or block transcription. If these changes are not repaired, they can lead to mutations and may contribute to cancer or disease, depending on which DNA sequences are affected. Nucleotide excision repair, or NER, is the process that detects and removes this kind of damage. Specialized proteins scan the DNA for a damaged region, then...

mutations

DNA Changes From Point Mutations to UV Damage

Mutations are changes in the DNA sequence. They can happen by chance during DNA copying, or they can be caused by environmental factors such as radiation and chemicals. Scientists also describe mutations by how much DNA they affect, how they change a protein, and whether they happen in body cells or germline cells. Some mutations affect only one nucleotide, which is a point mutation. When a point mutation falls inside a gene, the outcome depends on how the amino acid sequence changes. A silent...

transcription

Transcription and Gene Control

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translation

Protein Synthesis and mRNA Decoding

Protein synthesis begins when ribosomes decode messenger RNA (mRNA) and build a chain of amino acids. This final step of gene expression is called translation. The finished chain is a polypeptide, which can later become a functional protein. Proteins are often called the building blocks of life because they make up much of the body, from muscle fibers to hairs and immune system parts. The instructions for each protein are encoded in genes found in the DNA of every cell. In biology, the central...

bacterial transformation

Griffith’s Mouse Experiment and DNA

Bacterial transformation explains how DNA can move into bacteria and change their traits. Frederick Griffith first noticed this in 1928 while studying pneumonia-causing Streptococcus pneumoniae in mice. He compared one pathogenic strain with one non-pathogenic strain and found that only the pathogenic strain killed the host mice. Griffith made an unexpected discovery when he killed the pathogenic bacteria and mixed their remains with live, non-pathogenic bacteria. The mixture killed the mice,...

key terms and concepts

Learn how nucleotide excision repair fixes UV-induced DNA damage by cutting out lesions and replacing them with new DNA. Includes prokaryotes, humans, and XP.

DNA Damage Repair by Excision | JoVE K12

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Next Generation Science Standards

heredity-inheritance-and-variation-of-traits

Heredity: Inheritance and Variation of Traits

HS-LS3-2

new-york-state-science-learning-standards

New York State Science Learning Standards

Inheritance and Variation of Traits

HS-LS3-1.

The DNA Helix

Overview

Deoxyribonucleic acid, or DNA, is the genetic material responsible for passing traits from generation to generation in all organisms and most ...

DNA Packaging

Overview

Eukaryotes have large genomes compared to prokaryotes. In order to fit their genomes into a cell, eukaryotes must pack their DNA tightly inside ...

Organization of Genes

Overview

The genomes of eukaryotes can be structured in several functional categories. A strand of DNA is comprised of genes and intergenic regions. ...

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Describing the number and physical features of chromosomes can reveal abnormalities that underlie genetic diseases. This description is facilitated by ...

Replication in Prokaryotes

Overview

DNA replication has three main steps: initiation, elongation, and termination. Replication in prokaryotes begins when initiator proteins bind to ...

Replication in Eukaryotes

Overview

In eukaryotic cells, DNA replication is highly conserved and tightly regulated. Multiple linear chromosomes must be duplicated with high ...

Proofreading

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Mismatch Repair

Overview

Organisms are capable of detecting and fixing nucleotide mismatches that occur during DNA replication. This sophisticated process requires ...

Mutations

Overview

Mutations are changes in the sequence of DNA. These changes can occur spontaneously or they can be induced by exposure to environmental factors. ...

Transcription

Overview
Transcription is the process of synthesizing RNA from a DNA sequence by RNA polymerase. It is the first step in producing a protein from a gene ...

Translation

Lesson: Translation
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Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins which carry out the essential functions of life through systems of specialized cells.

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HS-LS1-3

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Forces Acting on Chromosomes

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HS-LS1-6

DNA Damage Repair by Excision

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