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

細胞分裂、または細胞周期の有糸分裂期は、成長因子やホルモンなどの外部化学刺激と、細胞周期調節因子などの内部因子によって制御されます。
細胞周期は、サイクリンと呼ばれるタンパク質とサイクリン依存性キナーゼ(Cdks)の組み合わせによって調節されています。サイクリンの濃度は、細胞周期のフェーズによって変動します。
細胞がG2期の終わりに近づくと、サイクリンBレベルが上昇します。高濃度では、サイクリンBはM期促進因子またはMPFと呼ばれるCdk1と複合体を形成します。
MPF活性は、細胞が分裂するかどうかを決定するリン酸化および脱リン酸化イベントによって制御されます。
G2が終了するまで、Wee1キナーゼはMPF上のチロシン残基をリン酸化し、MPFを不活性に保ちます。これにより、細胞周期の侵入を防ぎ、G2/M期で細胞を停止させます。
Cdc25がMPFを脱リン酸化すると、Cdk活性化キナーゼがMPF上の保存されたスレオニンをリン酸化して活性化します。
これで、細胞は有糸分裂を起こし、2つの娘細胞を産生します。

細胞分裂に影響を与える分子要素

細胞分裂の開始と抑制には、いくつかの外部および内部要因が影響を与えます。例えば、近隣細胞の死亡やヒト成長ホルモン（hGH）の放出は、細胞分裂を促進します。一方、hGHの不足や細胞の密集は細胞分裂を阻害することがあります。 いくつかのタンパク質は、各細胞周期のステージが正確に完了することを保証するための内部制御因子として機能しています。制御分子は直接的に作用するか、他の制御タンパク質の活性や産生に影響を与える場合があります。これらの制御分子は、細胞を次のフェーズに進める（陽性制御）またはサイクルを停止する（陰性制御）ことがあります。 陽性制御分子には、細胞周期の進行に必要なサイクリンとサイクリン依存性キナーゼ（Cdks）が含まれます。Cdksのレベルは一定のままでありながら、4つのサイクリン（サイクリンD、E、A＆B）のレベルは細胞周期のさまざまなフェーズで変動します。Cdkとしっかりと結合すると、サイクリンは活性化のためにリン酸化されます。サイクリンDのレベルはG1フェーズで上昇し、全体的に高い状態が続き、Mフェーズで減少します。サイクリンEのレベルはG1-Sフェーズの合流点で最高値に達し、サイクリンAはSフェーズとG2フェーズで高いレベルを示します。細胞がMフェーズに近づくと、サイクリンBのレベルが上昇し、細胞分裂を促進します。 陰性調節分子には、レチノブラストーマタンパク質（Rb）、p53、およびp21が含まれます。これらは細胞周期を停止します。例えば、p53はDNAの損傷を検出すると、DNA修復酵素を動員して損傷を修正します。DNAが未修復のままである場合、p53はアポトーシスまたは細胞死を引き起こし、損傷した染色体の複製を防ぎます。細胞内のp53レベルの増加は、p21の合成をも引き起こす可能性があります。p21はCdk/サイクリン複合体に結合し、サイクルの進行を停止させます。p53とp21の蓄積により、細胞はDNA合成（Sフェーズ）に進むことができなくなります。

 このテキストは、<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>から翻案されます。

いくつかの外部要因と内部要因が細胞分裂の開始と阻害に影響を与えます。たとえば、近くの細胞の死や...

Education

JoVE Core

Anatomy and Physiology

解剖生理学

Unit 1

ユニット1

Essential Cellular Processes

細胞の基本的プロセス

KEY TERMS AND CONCEPTS

主要用語と概念

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

Central Dogma: DNA to Protein

The central dogma explains how genetic information flows in cells from DNA to RNA to protein. It is a core idea in molecular biology and helps show how genes influence cell function. DNA stores the instructions. During transcription, a cell copies a gene into RNA, which is a related nucleic acid. That RNA message can then be used in translation to build a protein. Proteins carry out many jobs in cells and help determine traits. The central dogma links the genetic code in DNA to the molecules...

replication in eukaryotes

Eukaryotic DNA Copying at the Replication Fork

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types of rna

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transcription

Transcription and RNA Synthesis

Transcription is the process of making RNA from a DNA template. It is a key step in gene expression, because cells use the DNA sequence to build an RNA copy that can carry the message forward. During transcription, RNA polymerase binds to DNA and reads one strand as the template. The enzyme links RNA nucleotides together in the correct order to form a growing RNA molecule. This copying step does not make DNA; it produces RNA. The transcript focuses on the central idea of transcription as DNA...

translation

Translation: mRNA to Protein

Translation is the step in gene expression where ribosomes use messenger RNA, or mRNA, to build a protein. The mRNA sequence carries the instructions copied from DNA. During translation, those instructions are read in order so the cell can make a specific chain of amino acids. This process depends on the ribosome and transfer RNA, or tRNA. The ribosome reads the mRNA, and tRNA brings the matching amino acids. As the chain grows, the amino acids are linked together to form a polypeptide, which...

regulation of expression at multiple steps

regulation-of-expression-at-multiple-steps

How Cells Control Gene Expression

Cells control gene expression at several stages, from making RNA to building protein. These checkpoints include transcription, RNA processing, RNA localization, and translation. Together, they help decide when a gene is used and whether a protein is made. Transcription is controlled by regulatory proteins. Transcription factors, activators, and repressors can start or slow the transcription of genes. After transcription, the cell makes a precursor RNA, also called pre-mRNA. Pre-mRNA must be...

what is the cell cycle?

Cell Cycle Stages in Cell Growth

The cell cycle is the process that controls cell growth and division. It explains how one cell makes two new cells. This process helps cells grow and reproduce.

interphase

Interphase and Cell Growth

Interphase is the part of the cell cycle when a cell grows and prepares to divide. It is a major stage of the cell cycle, and it comes before cell division begins. During interphase, the cell carries out its normal functions. It also copies its DNA so each new cell can receive a full set of genetic material. The cell may also build up the materials it needs for division. Interphase is not a single step. It includes phases such as G1, S, and G2, which help the cell grow, copy DNA, and get...

mitosis and cytokinesis

Cell Division: Mitosis and Cytokinesis

Cell division depends on mitosis and cytokinesis. Mitosis is the stage when the cell’s nucleus divides and the copied chromosomes are separated into two sets. Cytokinesis is the step that follows and splits the cell into two daughter cells. These two processes work together to make sure each new cell receives genetic material and its own cytoplasm. Mitosis keeps the chromosome sets organized, while cytokinesis finishes the division of the whole cell. Together, they create two separate cells...

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

Cell Signaling Pathways and Responses

Cell signaling pathways and responses help cells communicate and react to changes. Cells send signals to one another, and those signals can trigger a specific response in the target cell. A signal usually begins when a signaling molecule reaches a cell with the right receptor, which is a protein that receives the message. The receptor helps the cell recognize the signal and start the communication process. Inside the cell, the message can move through a signaling pathway. This pathway passes...

types of signaling molecules

Chemical Messengers in Cell Signaling

Chemical messengers help cells communicate during signaling. These signaling molecules carry information from one cell to another and guide how cells respond. Some signaling molecules are gases, while others are proteins or peptides. Small lipids can also act as signals. In addition, cells may use steroids, amino acids, and even ions as signaling molecules. Each type of signaling molecule has different properties and works in a different way. Together, these molecules let cells send specific...

g protein-coupled receptors

G Protein-coupled Receptor Signaling

G protein-coupled receptors are a major class of cell-surface receptors. They help cells detect signals outside the cell and pass that information inward. These receptors are important in many kinds of cell communication. When a signal binds to a G protein-coupled receptor, the receptor changes shape. That change activates a G protein inside the cell. The activated G protein can then start a signaling pathway. This signaling system includes the receptor, the G protein, and the downstream...

cellular differentiation

From Stem Cell to Specialized Cells

Cellular differentiation turns unspecialized cells into specialized cells with specific jobs. This process helps a complex organism, such as a human, develop from a single fertilized egg into a body with many cell types. Nerve cells, muscle cells, and epithelial cells are examples of the final cell types that appear during development. A zygote is the first cell after fertilization. It is a totipotent stem cell, which means it has very high differentiation potential and can form all cell types...

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

anatomy and physiology

JoVE Core 解剖学と生理学では、人体の解剖学的および生理学的な詳細を、包括的で明確で魅力的なビデオ アニメーションで紹介します。このレッスン集は、人体の構造、コンポーネント、機能、要件に焦点を当てています。この知識を実際の医療および研究現場で応用することを実証する科学者による実際のビデオによって補完されています。

Characteristics of Life

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Develop and use a model to illustrate the hierarchical organization of interacting systems that provide specific functions within multicellular organisms. [Clarification Statement: Emphasis is on functions at the organism system level such as nutrient uptake, water delivery, and organism movement in response to neural stimuli. An example of an interacting system could be an artery depending on the proper function of elastic tissue and smooth muscle to regulate and deliver the proper amount of blood within the circulatory system.] [Assessment Boundary: Assessment does not include interactions and functions at the molecular or chemical reaction level.]

HS-LS1-2

Cell Cycle Regulators That Control Division

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