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

Podział komórki, czyli mitotyczna faza cyklu komórkowego, jest kontrolowana przez zewnętrzne bodźce chemiczne, takie jak czynniki wzrostu i hormony, oraz czynniki wewnętrzne, takie jak regulatory cyklu komórkowego.
Cykl komórkowy jest regulowany przez kombinację białek zwanych cyklinami i kinazami zależnymi od cyklin lub Cdk. Stężenia różnych cyklin zmieniają się w zależności od różnych faz cyklu komórkowego.
Gdy komórka zbliża się do końca fazy G2, poziom cykliny B wzrasta. W wysokich stężeniach cyklina B tworzy kompleks z Cdk1 zwany czynnikiem promującym fazę M lub MPF.
Aktywność MPF jest regulowana przez zdarzenia fosforylacji i defosforylacji, które określają, czy komórka ulega podziałowi, czy nie.
Do końca G2 kinaza Wee1 fosforyluje reszty tyrozyny na MPF i utrzymuje ją nieaktywną. Zapobiega to wejściu w cykl komórkowy i zatrzymuje ogniwo w fazie G2/M.
Gdy Cdc25 defosforyluje MPF, kinaza aktywująca Cdk fosforyluje konserwatywną treoninę na MPF i aktywuje ją.
Teraz komórki przechodzą mitozę i wytwarzają dwie komórki potomne.

czynniki molekularne wpływające na podział komórek

Wiele czynników, zarówno zewnętrznych, jak i wewnętrznych, wpływa na inicjację i zahamowanie podziału komórek. Na przykład, obumieranie sąsiednich komórek lub uwalnianie hormonu wzrostu człowieka (hGH) sprzyja podziałowi komórek, podczas gdy brak hGH lub zatłoczenie komórek może go powstrzymać.

Szereg białek pełni rolę wewnętrznych regulatorów, zapewniając, że każda faza cyklu komórkowego jest dokładnie ukończona przed przejściem do kolejnej. Cząsteczki regulacyjne mogą działać bezpośrednio lub wpływać na aktywność lub produkcję innych białek regulujących. Te cząsteczki regulacyjne mogą albo przyspieszać postęp komórki do kolejnej fazy (regulacja dodatnia), albo zatrzymywać cykl (regulacja negatywna).

Wśród cząsteczek regulujących dodatnich znajdują się cykliny oraz kinazy zależne od cyklin (Cdks), które są niezbędne dla postępu cyklu komórkowego. Choć poziom Cdks pozostaje stały, poziomy czterech cyklin (cyklina D, E, A i B) wahają się w różnych fazach cyklu. Po związaniu z Cdk, cyklina jest fosforylowana w celu aktywacji. Poziomy cykliny D rosną w fazie G1, pozostają wysokie przez cały czas i spadają w fazie M. Poziom cykliny E osiąga szczyt na skrzyżowaniu faz G1-S, podczas gdy cyklina A jest wysoka w fazach S i G2. W miarę zbliżania się komórki do fazy M, poziom cykliny B wzrasta i promuje podział komórki.

Wśród cząsteczek regulujących negatywnych znajdują się białko retinoblastomu (Rb), p53 i p21, które hamują cykl komórkowy. Na przykład, gdy p53 wykryje uszkodzenie DNA, enzymy naprawcze DNA są aktywowane w celu naprawienia uszkodzeń. Jeśli DNA nie zostanie naprawione, p53 uruchamia proces apoptozy lub śmierci komórki, uniemożliwiając uszkodzonemu podwójnemu powieleniu chromosomów. Zwiększenie poziomu p53 w komórce może również prowadzić do produkcji p21. P21 łączy się z kompleksem Cdk/cyklin i blokuje postęp cyklu. Nagromadzenie p53 i p21 uniemożliwia komórkom wejście w fazę syntezy DNA (faza S).

Ten tekst jest adaptacją z <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>

Czynniki Molekularne Wpływające na Podział Komórek

Na inicjację i hamowanie podziału komórek wpływa kilka czynników zewnętrznych i wewnętrznych. Na przykład śmierć pobliskich komórek lub uwolnienie ...

Education

JoVE Core

Anatomy and Physiology

Anatomia i fizjologia

Unit 1

Jednostka 1

Essential Cellular Processes

Podstawowe procesy komórkowe

KEY TERMS AND CONCEPTS

Kluczowe terminy i pojęcia

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

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

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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

Chemical Messengers in Cell Signaling

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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

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HS-LS1-2

Cell Cycle Regulators That Control Division

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