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

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From Molecules to Organisms: Structures and Processes

HS-LS1-4

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Molecular Factors Affecting Cell Division

La división celular, o la fase mitótica del ciclo celular, está controlada por estímulos químicos externos, como factores de crecimiento y hormonas, y factores internos, como los reguladores del ciclo celular.
El ciclo celular está regulado por una combinación de proteínas llamadas ciclinas y quinasas dependientes de ciclinas o Cdks. Las concentraciones de diferentes ciclinas fluctúan con las diferentes fases del ciclo celular.
A medida que una célula se acerca al final de la fase G2, el nivel de ciclina B aumenta. A altas concentraciones, la ciclina B forma un complejo con Cdk1 llamado factor promotor de la fase M o MPF.
La actividad de MPF está regulada por eventos de fosforilación y desfosforilación que determinan si la célula se divide o no.
Hasta el final de G2, la quinasa Wee1 fosforila los residuos de tirosina en el MPF y lo mantiene inactivo. Esto evita la entrada en el ciclo celular y detiene la celda en la fase G2/M.
Una vez que Cdc25 desfosforila el MPF, una quinasa activadora de Cdk fosforila una treonina conservada en el MPF y la activa.
Ahora las células se someten a mitosis y producen dos células hijas.

factores moleculares que afectan la división celular

Varios factores externos e internos influyen en la iniciación e inhibición de la división celular. Por ejemplo, la muerte de células cercanas o la liberación de la hormona del crecimiento humano (hGH) promueven la división celular. En contraste, la falta de hGH o el hacinamiento de células pueden inhibir la división celular.

Varias proteínas funcionan como reguladores internos para asegurar que cada etapa del ciclo celular se complete fielmente antes de pasar a la siguiente. Las moléculas reguladoras pueden actuar directamente o influir en la actividad o producción de otras proteínas reguladoras. Estas moléculas reguladoras promueven el progreso de la célula hacia la siguiente fase (regulación positiva) o detienen el ciclo (regulación negativa).

Las moléculas reguladoras positivas incluyen las ciclinas y las quinasas dependientes de ciclina (Cdks) que son esenciales para la progresión del ciclo celular. Mientras que el nivel de Cdks permanece constante, los niveles de cuatro ciclinas (ciclina D, E, A y B) fluctúan durante las diferentes fases del ciclo celular. Al unirse firmemente a Cdk, la ciclina se fosforila para su activación. Los niveles de la ciclina D aumentan en la fase G1, se mantienen altos durante todo el ciclo y disminuyen en la fase M. El nivel de la ciclina E alcanza su máximo en el punto de unión de la fase G1-S, mientras que la ciclina A es alta durante las fases S y G2. A medida que la célula se acerca a la fase M, el nivel de la ciclina B aumenta y promueve la división celular.

Las moléculas reguladoras negativas incluyen la proteína del retinoblastoma (Rb), p53 y p21, que detienen el ciclo celular. Por ejemplo, cuando p53 detecta daño en el ADN, se reclutan enzimas de reparación del ADN para corregir el daño. Si el ADN no se repara, p53 inicia la apoptosis o muerte celular y evita la duplicación de cromosomas dañados. El aumento del nivel de p53 en la célula también puede desencadenar la síntesis de p21. El p21 se une al complejo Cdk/ciclina y detiene la progresión del ciclo. La acumulación de p53 y p21 evita que las células avancen a la síntesis de ADN (la fase S).

Este texto está parcialmente adaptado de <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>

Factores moleculares que afectan la división celular

Varios factores externos e internos influyen en el inicio e inhibición de la división celular. Por ejemplo, la muerte de las células cercanas o la liberación de ...

Education

Educación

JoVE Core

Anatomy and Physiology

Anatomía y Fisiología

Unit 1

Unidad 1

Essential Cellular Processes

Procesos celulares esenciales

KEY TERMS AND CONCEPTS

TÉRMINOS Y CONCEPTOS CLAVE

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

RNA Types in Gene Expression

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transcription

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translation

Translation: mRNA to Protein

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regulation of expression at multiple steps

regulation-of-expression-at-multiple-steps

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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

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g protein-coupled receptors

G Protein-coupled Receptor Signaling

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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

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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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