Name: condensin proteins in chromosome packing
Uploaded: 2023-04-30T18:28:50.000Z
Duration: 2 min 15 s
Channel: JoVE

K12 Standards

Pennsylvania State Academic Standards

9-12

Life Science

Inheritance and Variation of Traits

3.1.9-12.D

Condensins

Fundamentalną częścią życia jest zdolność komórki do replikacji swojego genomu i podziału; procesy te zachodzą w dwóch głównych fazach cyklu komórkowego.
Po pierwsze, w fazie S chromosomalne DNA ulega duplikacji. Podczas fazy M zduplikowane chromosomy są rozdzielane i dystrybuowane do dwóch genetycznie identycznych komórek potomnych.
Po fazie S DNA chromatyd siostrzanych jest bardzo długie i splątane. Oddzielenie chromatyd siostrzanych w tym stanie może prowadzić do pęknięć chromosomów, nieprawidłowej segregacji, a nawet śmierci komórki.
Aby zapobiec temu potencjalnemu kryzysowi, komórka poświęca znaczną ilość energii podczas wczesnej mitozy na stopniową reorganizację siostrzanych chromatyd w krótsze struktury, które łatwiej się rozdzielają.
Ta reorganizacja opiera się na kondensinie, kompleksie białkowym biorącym udział w kondensacji chromosomów.
Kondensacja składa się z pięciu podjednostek. U eukariontów dwie główne podjednostki, SMC2 i SMC4, są połączone w swoich domenach głównych ATPazy przez trzy pozostałe podjednostki: jedną podjednostkę kleizyny i dwie podjednostki powtórzeń HEAT.
Kondensyny wykorzystują energię generowaną przez hydrolizę ATP do promowania dwóch głównych procesów, które ułatwiają separację chromatyd siostrzanych: kondensacji chromosomów i rozdzielczości chromatyd siostrzanych.
Podczas kondensacji chromosomów chromatydy stają się ciasno upakowane. Podczas rozdzielczości chromatyd siostrzanych, skondensowane chromatydy siostrzane stają się odrębnymi strukturami, gdy siostrzane DNA są rozłączane lub dekatenowane przez częściowe usunięcie kohezyn.
Zanim komórka osiągnie metafazę, chromatydy siostrzane są tylko luźno połączone wzdłuż ramion, ale nadal są ściśle połączone w centromerach. 
Kondensyna może zmieniać zwijanie DNA i katalizować kondensację chromosomów oraz rozdzielczość chromatyd siostrzanych poprzez tworzenie pierścieniowych struktur, które otaczają pętle DNA.

<ol>
	<li>Batty, Paul i Daniel W. Gerlichowie. 2019. "Mechanika chromosomów mitotycznych: jak komórki segregują swój genom." Trendy w biologii komórki 29 (9): 717–26. https://doi.org/10.1016/j.tcb.2019.05.007. </li>
	<li>Skibbens, Robert V. 2019. "Kondensyny i kohezyny – jedna z tych rzeczy nie jest taka sama jak druga!" Dziennik Nauki o Komórkach 132 (3). https://doi.org/10.1242/jcs.220491. </li>
</ol>

kondensyny

Kondensyny to duże kompleksy białkowe, które wykorzystują ATP do napędzania składania chromosomów podczas mitozy. Przekształcają splątaną, bezkształtną masę pointerfazowego DNA w zindywidualizowane chromosomy poprzez zagęszczanie, organizowanie i segregację chromosomalnego DNA. Komórki roślinne i zwierzęce zawierają dwa rodzaje kompleksów kondensynowych – kondensynę I i kondensynę II. Obydwa kompleksy mają pięć podjednostek: dwie podjednostki SMC (Structural Maintenance of Chromosomy), podjednostkę Kleisina i dwie podjednostki HEAT-repeat. Podstawowymi podjednostkami zarówno kondensyny I, jak i kondensyny II są SMC2 i SMC4. Białka SMC zmieniają układ DNA w sposób zależny od ATP. Pozostałe trzy podjednostki - podjednostki inne niż SMC lub pomocnicze - różnią się między tymi dwoma kompleksami. Badania, w których wyczerpano się kondensyny kręgowców, wykazały odrębną rolę kondensyn I i II w tworzeniu chromosomów mitotycznych. Usunięcie kondensyny II skutkuje dłuższymi, bardziej elastycznymi chromosomami, splątaniem chromosomów, nieporęcznymi mostkami chromatyny podczas anafazy i drastycznym skróceniem profazy. Natomiast usunięcie kondensyny I prowadzi do krótszych, szerszych chromosomów i zakłócenia anafazy, które jest mniej poważne, ale nadal skutkuje niepowodzeniem cytokinezy. Popularnym wyjaśnieniem sposobu, w jaki kondensyny zagęszczają chromosomy, jest model wytłaczania pętlowego. Model ten zakłada, że cząsteczka kondensyny może wiązać się z dwoma pobliskimi miejscami DNA i przesuwać je w przeciwnych kierunkach, tworząc rosnącą pętlę DNA. Kondensyny mogą również oddziaływać ze sobą, tworząc multimery łączące odległe segmenty chromatyny. Mutacje kondensyny powiązano z kilkoma typami nowotworów. Na przykład u myszy z mutacją zmiany sensu w genie podjednostki kondensyny II rozwinął się chłoniak z komórek T. Chociaż mechanizmy, poprzez które kondensyny wpływają na architekturę chromosomów, są wciąż wyjaśniane, te kompleksy białkowe są integralną częścią cyklu komórkowego i przeżycia komórek.

Kondensyny

Kondensyny to duże kompleksy białkowe, które wykorzystują ATP do napędzania składania chromosomów podczas mitozy. Przekształcają splątaną, bezkształtną masę ...

Education

JoVE Core

Cell Biology

Biologia komórki

Unit 1

Jednostka 1

Cell Division

Podział komórkowy

KEY TERMS AND CONCEPTS

Kluczowe terminy i pojęcia

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 and easier to handle inside the cell.

Condensin Proteins in Chromosome Packing

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 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

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...

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 condensin proteins help condense DNA into chromosomes during cell division. This high school overview links chromosome packing to accurate cell division.

Condensin Proteins in Chromosome Packing | JoVE K12

cell biology

JoVE Core Cell Biology illustrates complex cellular processes in easy-to-understand yet comprehensive animated video lessons. This collection focuses on the essential components and functions of cells, including organelles and membranes, cellular transport, and cell energetics. It is complemented by scientist-in-action videos that demonstrate the application of cell biology in real-world research experiments.

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

Next Generation Science Standards

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.

new-york-state-science-learning-standards

New York State Science Learning Standards

HS-LS1-4.

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3.1.9-12.P

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3.1.9-12.Q

Condensin Proteins in Chromosome Packing

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