Name: chromatid pulling in cell division
Uploaded: 2023-04-30T18:28:50.000Z
Duration: 2 min 17 s
Channel: JoVE

K12 Standards

Pennsylvania State Academic Standards

9-12

Life Science

Inheritance and Variation of Traits

3.1.9-12.D

Separation of Sister Chromatids

À la fin de la métaphase, les chromosomes bi-orientés s’alignent sur la plaque de métaphase. Au cours de cette phase, les complexes cycliques de la protéine de cohésine maintiennent les chromatides sœurs ensemble dans la région du centromère et les empêchent d’être séparées.
La progression de la métaphase à l’anaphase est déclenchée par la phosphorylation induite par la cycline-Cdk d’une enzyme ubiquitine ligase multi-sous-unitaire – le complexe favorisant l’anaphase, également connu sous le nom de cyclosome ou APC/C. L’APC/C phosphorylée se lie à une protéine, Cdc20, formant un complexe actif.
Le complexe actif APC/C reconnaît une protéine inhibitrice appelée securine qui est liée à une enzyme protéase appelée séparose. Avant cette reconnaissance, la securine inhibe l’activité de la séparose.
Le complexe actif APC/C marque la securine avec la protéine ubiquitine, la ciblant pour la dégradation protéasomale. La destruction de la securine libère des séparations.
Le complexe cycline-Cdk régule également négativement l’activité de la séparation non liée par phosphorylation inhibitrice.
Le complexe actif APC/C provoque l’ubiquitination des cyclines, les ciblant pour la dégradation du protéasome. La destruction de la cycline supprime l’activité enzymatique des kinases dépendantes des cyclines ou Cdk.
L’inactivation de Cdks permet aux enzymes phosphatases de déphosphoryler la séparase et empêche la rephosphorylation inhibitrice de la séparase médiée par Cdk. La déphosphorylation permet à l’enzyme séparatrice de cliver le complexe cyclique de cohésine qui maintient les chromatides sœurs ensemble.
Le clivage de la cohésine entraîne la perte absolue de la cohésion des chromatides sœurs, marquant la transition de la métaphase à l’anaphase. La perte de cohésion permet aux chromatides sœurs de se séparer et de se déplacer vers les pôles opposés du fuseau.

<ol>
	<li>Claire Acquaviva et Jonathon Pines. 20016. « Le complexe/cyclosome favorisant l’anaphase : APC / C ». Journal des sciences cellulaires. 119: 2401-2404. [<a href="https://jcs.biologists.org/content/119/12/2401#sec-2">Source</a>]</li>
	<li>Frank Uhlmann, Friedrich Lottspeich et Kim Nasmyth. 1999. « La séparation des chromatides sœurs au début de l’anaphase est favorisée par le clivage de la sous-unité de cohésine Scc1. » Nature 400 (6739). Nature Publishing Group : 37 à 42. [<a href="https://mcb.berkeley.edu/courses/mcb230/WEB/PAPERS/SCC1.pdf">Source</a>]</li>
	<li>Farr, Katie A., et Orna Cohen‐Fix. « La transition de la métaphase à l’anaphase : un cas de destruction productive. » Revue européenne de biochimie 263, n° 1 (1999) : 14-19.</li>
	<li>Fang, Guowei, Hongtao Yu et W. Kirschner. « Contrôle des transitions mitotiques par le complexe favorisant l’anaphase. » Transactions philosophiques de la Royal Society de Londres. Série B : Sciences biologiques 354, n° 1389 (1999) : 1583-1590.</li>
</ol>

séparation des chromatides sœurs

Lors de la transition de la prophase à la métaphase, il y a une réduction de la cohésion le long des bras chromosomiques, entraînant la résolution des chromatides sœurs. Cependant, des connexions de cohésine résiduelles subsistent pour maintenir les chromatides sœurs ensemble jusqu'à la transition de la métaphase à l'anaphase. La connexion résiduelle évite toute séparation prématurée des chromatides sœurs, bloquant les risques d'aneuploïdie au sein des cellules filles.

Au début de l’anaphase, la séparase, une enzyme protéolytique, est activée. La séparase activée clive la sous-unité Scc1 des anneaux de cohésine résiduels, entraînant une perte totale de cohésion. Les chromatides sœurs se séparent en l’absence de force pour les maintenir ensemble. Le manque de cohésion permet aux forces dirigées vers les pôles, s'exerçant le long des microtubules, de tirer les chromatides séparées vers les pôles du fuseau.

Au début de la mitose, le point de contrôle de l'assemblage du fuseau (SAC) interdit au complexe promoteur de l'anaphase ou cyclosome (APC/C) d'ubiquitiner les protéines, telles que la sécurine et les cyclines de la phase M, dont la dégradation est nécessaire à l'anaphase. Ce n'est que lorsque chaque chromosome s'aligne correctement sur le fuseau mitotique que le SAC est désactivé pour permettre la phosphorylation et l'activation des sous-unités régulatrices APC/C - CDC20 et CDH1.

Le CDC20 est phosphorylé par Cdk1/cycline B pour former l'APC/C-CDC20 actif. L'APC/C-CDC20 actif catalyse ensuite la dégradation de la sécurine, de la cycline A et de la cycline B pour favoriser la transition anaphase. L’activité de Cdk étant dépendante de la cycline, la dégradation de la cycline B entraîne la perte de l’activité de Cdk1. La perte du complexe Cdk1/cycline B inactive APC/C-CDC20 mais active une autre sous-unité régulatrice, APC/C-CDH1, qui signale l'achèvement de la transition métaphase-anaphase. L'APC/C-CDH1 actif facilite la sortie mitotique et stabilise la phase G1 suivante en empêchant l'accumulation prématurée de cyclines mitotiques.

Le basculement des activités d’APC/C-CDC20 et d’APC/C-CDH1 a deux conséquences importantes. Premièrement, ces sous-unités régulatrices déclenchent des spécificités de substrat qui se chevauchent mais qui sont distinctes et favorisent ainsi une transition ordonnée du cycle cellulaire. Deuxièmement, CDC20 et CDH1 sont régulés par différents mécanismes. Lorsque APC/C-CDC20 est actif, CDH1 subit une phosphorylation inhibitrice par la cycline B/Cdk1, l'empêchant de se lier à APC/C. En revanche, l'activité CDC20 est inhibée par un complexe de points de contrôle mitotique, une multiprotéine (BUBR1, BUB3, CDC20 et MAD2) activée par le SAC.

Séparation des chromatides sœurs

Lors de la transition de la prophase à la métaphase, il y a une réduction de la cohésion le long des bras chromosomiques, ce qui entraîne la résolution de la ...

Education

Enseignement

JoVE Core

Cell Biology

Biologie cellulaire

Unit 1

Unité 1

Cell Division

Division cellulaire

KEY TERMS AND CONCEPTS

TERMES ET CONCEPTS CLÉS

chromatid pulling in cell division

Separation of sister chromatids is a key step in cell division. Sister chromatids are two identical copies of a chromosome that stay attached until the cell is ready to split them apart. Their separation helps each new cell receive the correct genetic material.

During this stage, the sister chromatids are pulled to opposite sides of the cell. This movement happens as the cell prepares to divide into two daughter cells. Once the chromatids separate, each side of the cell has a complete set of chromosomes.

This process is essential for accurate chromosome distribution. If sister chromatids do not separate properly, the new cells may not get the right genetic information. Understanding this step helps explain how cells copy and pass on DNA during division.

Chromatid Pulling in Cell Division

mitosis and cytokinesis

Stages of Cell Division in Eukaryotes

Cell division in eukaryotes follows a tightly regulated cycle that includes cell growth, DNA replication, chromosome duplication, chromosome distribution to daughter cells, and cell division. Regulatory systems and extracellular signals help control when cells divide. In typical human cells, the cycle takes about 24 hours. The cycle has two major stages. DNA is copied during the S phase of interphase. The mitotic, or M, phase then separates the duplicated chromosomes into two new nuclei and...

chromosome duplication

Chromosome Copying in Cell Division

Chromosome copying is an important step in cell division. Before a cell divides, it must make an exact copy of its chromosomes so each new cell can receive the same genetic information. A chromosome is a DNA-containing structure that carries genes. During duplication, the chromosome is copied into two identical sister chromatids. These copies stay attached until the cell is ready to separate them. This process helps ensure that daughter cells inherit a complete set of chromosomes. Accurate...

cohesins

Cohesins in Sister Chromatid Separation

Cohesins are protein complexes that help hold sister chromatids together after DNA is copied. They play a key role in cell division by keeping the two copies of a chromosome connected until the right time. These proteins act like a link between the sister chromatids. When the cell is ready to separate them, cohesins must be removed or released so each new cell can get one complete set of chromosomes. Cohesins are an important part of chromosome behavior during mitosis and meiosis. Their...

condensins

Condensin Proteins in Chromosome Packing

Condensin proteins help pack DNA into condensed chromosomes during cell division. They are part of the larger set of proteins that organize genetic material so it can be separated correctly when a cell divides. These proteins act by shaping and tightening chromosome structure. This process is important because DNA must be compacted before it can move through the stages of division. Condensins are therefore closely linked to chromosome condensation, the step that makes chromosomes more compact...

the mitotic spindle

How the Mitotic Spindle Guides Cell Division

The mitotic spindle guides chromosome movement during cell division. It is a structure made of microtubules, which are thin protein fibers in the cell. These fibers organize and help separate the genetic material before the cell splits. The spindle forms as the cell prepares to divide. Its fibers attach to chromosomes and line them up so they can be moved apart in an orderly way. This careful organization helps each new cell receive the correct set of chromosomes. The mitotic spindle is a key...

centrosome duplication

Centrosome Duplication in Cell Division

Centrosome duplication is an important step in cell division. The centrosome helps organize the cell’s internal structure, and it must be copied before a cell divides.

spindle assembly

Spindle Formation in Cell Division

Spindle formation in cell division is the process that builds the microtubule-based spindle needed to separate chromosomes. Microtubules are long protein fibers that help move and organize cell parts during division. During this process, microtubules grow and are arranged into a spindle structure around the chromosomes. The spindle forms in a way that supports chromosome movement to opposite sides of the cell. This step is essential for accurate cell division. Spindle formation depends on the...

attachment of sister chromatids

Sister Chromatid Attachment in Mitosis

Sister chromatid attachment in mitosis helps align duplicated chromosomes before they separate. Sister chromatids are the matching copies made after DNA replication. They stay connected until the cell is ready to divide. The attachment step is closely tied to the metaphase plate, the middle of the cell where chromosomes line up. This alignment helps each new cell receive one copy of every chromosome. Proper attachment is an important part of accurate cell division.

forces acting on chromosomes

Chromosome Movement During Cell Division

Chromosome movement during cell division depends on forces that act on the chromosomes. These forces help move the chromosomes into the right position as the cell divides. The transcript focuses on how these forces affect chromosome behavior during division. It highlights the role of the mitotic spindle, which is the structure that helps organize and move chromosomes. The spindle uses force to guide chromosome movement at the right time. Understanding these forces helps explain how...

separation of sister chromatids

Separation of sister chromatids is a key step in cell division. Sister chromatids are two identical copies of a chromosome that stay attached until the cell is ready to split them apart. Their separation helps each new cell receive the correct genetic material. During this stage, the sister chromatids are pulled to opposite sides of the cell. This movement happens as the cell prepares to divide into two daughter cells. Once the chromatids separate, each side of the cell has a complete set of...

the spindle assembly checkpoint

How Cells Verify Chromosome Spindle Attachment

The spindle assembly checkpoint helps cells verify that chromosomes are attached to the spindle before division continues. It acts as a safety step during cell division and helps prevent errors in chromosome separation. This checkpoint is controlled by kinetochores, which are protein structures on chromosomes that connect to spindle fibers. If a chromosome is not attached correctly, the checkpoint can delay progression until the problem is fixed. Once the attachment is correct, the cell can...

anaphase a and b

Chromosome and Spindle Movement in Anaphase

Anaphase is the stage of cell division when chromosomes move apart. In this phase, sister chromatids separate and travel toward opposite poles of the cell. Chromosome movement in anaphase can happen in two ways. In anaphase A, chromosomes move closer to the poles as the microtubules attached to them shorten. In anaphase B, the spindle poles themselves move farther apart and help stretch the cell. These two movements work together to ensure that the separated chromosomes are pulled to opposite...

anaphase promoting complex

Cell Cycle Control by APC

The anaphase-promoting complex, or APC, helps control cell cycle progression. It acts during cell division to help move the process from one stage to the next. This control is important for proper timing in the cell cycle. APC is a protein complex that works as a regulator. It helps trigger key steps that allow division to continue in an ordered way. By guiding this transition, APC supports normal cell cycle control.

the contractile ring

Cell Division and the Contractile Ring

The contractile ring helps cells divide at the end of cell division. It forms at the cell's center and tightens to split one cell into two. This process is part of cytokinesis, the stage when the cytoplasm divides. The ring is made of actin and myosin, two proteins that can work together to create force. As the ring contracts, it draws the cell membrane inward. This pinch helps separate the two daughter cells. Understanding the contractile ring is important for studying how cells complete...

determining the plane of cell division

Spindle Position and Cell Division Plane

The plane of cell division is set by the position of the spindle during mitosis. Cells use this internal structure to help decide where the cell will split. The result affects how the two daughter cells are arranged after division. This process is important in many developing tissues. It helps explain how cells divide in a controlled direction. A clear plane of division supports proper cell organization as new cells form. The transcript focuses on how the spindle is used to determine that...

the phragmoplast

Phragmoplast in Plant Cell Division

The phragmoplast is a plant cell structure that forms during cell division. It helps guide the final stage of division, when the cell begins to split into two daughter cells. In plant cells, the phragmoplast appears between the two new nuclei. It is part of the process that leads to the formation of a new cell wall. This wall separates the daughter cells after division is complete. The phragmoplast plays an important role in plant cytokinesis, which is the physical division of the cytoplasm.

distribution of cytoplasmic content

Cytoplasmic Content During Cell Division

Cytoplasmic content is distributed as a cell divides. This process helps each new cell receive the materials it needs to function. The cytoplasm includes the fluid and structures inside the cell membrane, but outside the nucleus. During cell division, this content is separated between the two daughter cells. The division must be organized so both cells can continue normal activity after the split. The video focuses on how this distribution occurs as part of cell division. It highlights the...

key terms and concepts

Learn how sister chromatids separate during cell division and move to opposite sides of the cell so daughter cells receive the correct genetic material.

Chromatid Pulling in Cell Division | JoVE K12

cell biology

JoVE Core Biologie cellulaire illustre les processus cellulaires complexes dans des leçons vidéos complètes mais faciles à comprendre. Cette collection se concentre sur les composants et fonctions essentiels de la cellule ; cela inclut les organelles et les membranes ainsi que le transport et le métabolisme énergétique cellulaire. Elle est complétée par nos vidéos de scientifiques à l'action qui démontrent l'application de la biologie cellulaire dans des expériences concrètes.

Louisiana Student Standards for Science

High School

Life Sciences

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

From Molecules To Organisms: Structures And Processes

HS-LS1-4

Tennessee Academic Standards

Biology

From Molecules to Organisms: Structures and Processes

BIO1.LS1.6

Minnesota Academic Standards in Science

3.1.1 9L.3.1.1.2

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

New Jersey Student Learning Standards for Science

Arizona Science Standards

HS+B.L1

HS+B.L1U1.9

Alabama Course of Study Science

9-12.B.1.3

Florida Department of Education

SC.912.L.16

SC.912.L.16.14

south-carolina-college-and-career-ready-science-standards

South Carolina College and Career Ready Science Standards

B-LS1-4.

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3.1.9-12.P

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3.1.9-12.Q

Chromatid Pulling in Cell Division

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