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

细胞分裂，即细胞周期的有丝分裂阶段，受到生长因子和激素等外部化学信号以及细胞周期调控因子等内部因素的调控。
细胞周期由一组称为周期蛋白（cyclins）和周期蛋白依赖性激酶（cyclin-dependent kinases，Cdks）的蛋白质共同调控。不同周期蛋白的浓度随着细胞周期各时相的变化而波动。
当细胞接近G2期结束时，细胞周期蛋白B的水平上升。在高浓度下，细胞周期蛋白B与Cdk1结合形成复合物，称为M期促进因子（MPF）。
MPF 活性受到磷酸化和去磷酸化事件的调控，这些事件决定了细胞是否进行分裂。
直到G2期末，Wee1激酶会磷酸化MPF上的酪氨酸残基，使其保持非活性状态。这可以阻止细胞进入细胞周期，并将细胞阻滞在G2/M期交界处。
一旦Cdc25使MPF去磷酸化，一种Cdk激活激酶就会磷酸化MPF上一个保守的苏氨酸残基，从而激活MPF。
现在细胞进行有丝分裂，产生两个子细胞。&#160;

影响细胞分裂的分子因素

许多外部和内部因素都影响着细胞分裂的启动和抑制。例如，细胞附近的死亡或人类生长激素（hGH）的释放能够促进细胞的分裂。相反，缺乏hGH或拥挤的细胞可以用来抑制细胞分裂。

几种蛋白质可以作为内部的调节因子，用来确保每个细胞的阶段性周期在进入下一阶段之前能够可靠的完成。调节分子可以直接作用或影响到其他蛋白质的活性。这些调节分子要么是促进细胞进入到下一个阶段（正调控），要么是阻止细胞进入到下一个阶段（负调控）。

正调节分子包括周期蛋白和周期依赖性激酶（Cdks），它们对于细胞周期的进展至关重要。虽然Cdks的水平保持不变，但四种周期蛋白（蛋白D，E，A和B）的水平在细胞周期中的不同阶段产生波动。当周期蛋白与Cdk紧密结合后，周期蛋白会被磷酸化以激活。蛋白D的水平在G1期得到上升，保持着较高的水平并在M期发生下降。蛋白E的水平在G1-S期的交界处达到峰值，而蛋白A则在S期和G2期处于高水平状态。随着细胞的周期接近M期，蛋白B的水平得到上升的同时也促进了细胞分裂。

负调节分子包括视网膜母细胞瘤蛋白（Rb），p53和p21，它们会阻止细胞周期。例如，当p53检测到DNA损伤时，它们吸收DNA修复酶来纠正损伤。如果DNA仍未被修复，p53将会启动凋亡过程或让细胞死亡，同时并阻止已损坏染色体的复制。细胞中p53水平的增加也可能会触发p21的合成。p21与Cdk或周期蛋白复合物互相结合并阻止周期的进行。累积的p53和p21能够有效的防止细胞进入DNA合成期（S期）。

本文改编自 <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>

多种外部和内部因素影响细胞分裂的启动与抑制。例如，邻近细胞的死亡或某些物质的释放……

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JoVE Core

Anatomy and Physiology

解剖学与生理学

Unit 1

第 1 单元

Essential Cellular Processes

细胞基本过程

KEY TERMS AND CONCEPTS

关键术语与概念

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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Interphase and Cell Growth

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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

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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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