Name: cell cycle regulators that control division
Uploaded: 2023-06-23T15:38:45.000Z
Duration: 1 min 27 s
Channel: JoVE

K12 Standards

Next Generation Science Standards

High School

Life Science

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

From Molecules to Organisms: Structures and Processes

HS-LS1-4

molecular-factors-affecting-cell-division

Molecular Factors Affecting Cell Division

Деление клеток, или митотическая фаза клеточного цикла, контролируется внешними химическими стимулами, такими как факторы роста и гормоны, и внутренними факторами, такими как регуляторы клеточного цикла.
Клеточный цикл регулируется комбинацией белков, называемых циклинами, и циклин-зависимыми киназами или Cdk. Концентрации различных циклинов колеблются в зависимости от фаз клеточного цикла.
По мере того, как клетка приближается к концу фазы G2, уровень циклина B повышается. В высоких концентрациях циклин B образует комплекс с Cdk1, называемый фактором, способствующим М-фазе или MPF.
Активность MPF регулируется событиями фосфорилирования и дефосфорилирования, которые определяют, подвергается ли клетка делению или нет.
До конца G2 киназа Wee1 фосфорилирует остатки тирозина на MPF и поддерживает его в неактивном состоянии. Это предотвращает вступление в клеточный цикл и останавливает ячейку в фазе G2/M.
Как только Cdc25 дефосфорилирует MPF, Cdk-активирующая киназа фосфорилирует консервативный треонин на MPF и активирует его.
Теперь клетки подвергаются митозу и производят две дочерние клетки.

Молекулярные факторы, влияющие на деление клеток

Несколько внешних и внутренних факторов оказывают влияние на инициацию и ингибирование деления клеток. Например, гибель окружающих клеток или высвобождение гормона роста человека (hGH) способствует делению клеток. В противоположность этому, недостаток (hGH) или скученность клеток могут ингибировать деление.

Несколько белков выполняют функцию внутренних регуляторов, чтобы обеспечить исполнение каждой стадии клеточного цикла перед переходом к следующей. Молекулы-регуляторы могут действовать непосредственно или влиять на активность или производство других регуляторных белков. Эти регуляторные молекулы либо способствуют прогрессированию клетки к следующей фазе (положительная регуляция), либо останавливают цикл (отрицательная регуляция).

Молекулы положительной регуляции включают циклины и циклин-зависимые киназы (Cdks), которые являются необходимыми для прогрессирования клеточного цикла. В то время как уровень Cdks остается постоянным, уровни четырёх циклинов (циклина D, E, A и B) колеблются в различных фазах клеточного цикла. При тесном связывании с Cdk, циклин фосфорилируется для активации. Уровень циклина D повышается в фазе G1, остается высоким в течение всего цикла и снижается в фазе M. Уровень циклина E достигает пика на переходе от фазы G1 в S, в то время как циклин A повышается в фазах S и G2. При приближении клетки к фазе M уровень циклина B повышается и способствует делению клеток.

Молекулы отрицательной регуляции включают белки ретинобластомы (Rb), p53 и p21, которые прерывают клеточный цикл. Например, когда p53 обнаруживает повреждение ДНК, ДНК-ремонтные ферменты набираются для исправления повреждения. Если ДНК остаётся невостановленной, p53 инициирует апоптоз или клеточную смерть и предотвращает дублирование повреждённых хромосом. Повышенный уровень p53 в клетке также может спровоцировать синтез p21. P21 связывается с комплексами Cdk/циклин и останавливает прогрессирование цикла. Накопление p53 и p21 препятствует прохождению клеток к синтезу ДНК (в фазе S).

Адаптированная версия текста <a href="https://openstax.org/books/biology-2e/pages/10-3-control-of-the-cell-cycle">Openstax, Anatomy and Physiology 2e, Section 10.3: Control of the Cell Cycle</a>

Несколько внешних и внутренних факторов влияют на инициацию и ингибирование деления клеток. Например, гибель близлежащих клеток или высвобождение ...

Education

JoVE Core

Anatomy and Physiology

Анатомия и физиология

Unit 1

Раздел 1

Essential Cellular Processes

Основные клеточные процессы

KEY TERMS AND CONCEPTS

ОСНОВНЫЕ ТЕРМИНЫ И ПОНЯТИЯ

cell cycle regulators that control division

Cell division is controlled by outside signals and by internal cell cycle regulators. Nearby cell death can encourage division, and human growth hormone (hGH) can also promote it. In contrast, too little hGH or crowded cells can slow or stop division.

Inside the cell, regulator molecules help each stage finish correctly before the next stage begins. Some regulators act directly on the cycle, while others affect the activity or production of other regulatory proteins. These molecules can either push the cell forward, which is positive regulation, or stop the cycle, which is negative regulation.

The main positive regulators are cyclins and cyclin-dependent kinases, or Cdks. Cdks stay at a constant level, while cyclin levels rise and fall during the cell cycle. The four cyclins are cyclin D, cyclin E, cyclin A, and cyclin B. When cyclins bind tightly to Cdks, the complex becomes active after phosphorylation.

Each cyclin acts at a different point in the cycle. Cyclin D rises in G1, stays high through most of the cycle, and drops in M phase. Cyclin E peaks at the G1-S transition. Cyclin A is high during S and G2, and cyclin B rises as the cell nears M phase and helps drive cell division.

Negative regulators help prevent damaged or uncontrolled division. These include retinoblastoma protein, or Rb, p53, and p21. When p53 detects DNA damage, it recruits DNA repair enzymes. If the damage is not repaired, p53 can trigger apoptosis, or cell death, and prevent damaged chromosomes from being copied.

p53 can also increase p21 synthesis. The p21 protein binds to the Cdk/cyclin complex and blocks cycle progression. Together, p53 and p21 can stop the cell from entering DNA synthesis, which is the S phase.

Cell Cycle Regulators That Control Division

cell-cycle-regulators-that-control-division

the central dogma

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Eukaryotic DNA Copying at the Replication Fork

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transcription

Transcription and RNA Synthesis

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Translation: mRNA to Protein

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regulation of expression at multiple steps

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Cell Cycle Stages in Cell Growth

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Interphase and Cell Growth

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mitosis and cytokinesis

Cell Division: Mitosis and Cytokinesis

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the cell cycle control system

Cell Cycle Checkpoints and Cyclin Control

The cell cycle is controlled by checkpoints that help a cell move from one phase to the next and begin mitosis. This control system uses internal regulatory molecules and outside signals to send stop or advance instructions. It makes sure each step is finished before the cell moves forward. Cyclins and cyclin-dependent kinases, or Cdks, are the main regulators of the cell cycle. They act during the G1, G2, and M phases. These regulators work at specific checkpoints to keep cell division...

molecular factors affecting cell division

Cell division is controlled by outside signals and by internal cell cycle regulators. Nearby cell death can encourage division, and human growth hormone (hGH) can also promote it. In contrast, too little hGH or crowded cells can slow or stop division. Inside the cell, regulator molecules help each stage finish correctly before the next stage begins. Some regulators act directly on the cycle, while others affect the activity or production of other regulatory proteins. These molecules can either...

what is meiosis?

Meiosis and the Formation of Gametes

Meiosis is the cell division process that forms gametes, or sex cells. It reduces the chromosome number so offspring can inherit the correct amount of genetic material. This process includes two successive divisions. First, one cell divides, and then the resulting cells divide again. These steps separate the genetic material in a controlled way. Meiosis helps explain how sexual reproduction passes traits from one generation to the next. It is a key topic in high school biology because it...

overview of cell signaling

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key terms and concepts

Learn how external signals, cyclins, Cdks, p53, and p21 control cell division and help cells decide when to divide or stop.

Cell Cycle Regulators That Control Division | JoVE K12

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HS-LS1-2

Cell Cycle Regulators That Control Division

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