Name: cyclins and cdks in the cell cycle
Uploaded: 2019-03-11T09:21:14.000Z
Duration: 1 min 45 s
Channel: JoVE

K12 Standards

Virginia  Standards of Learning

HIgh School

Biology

BIO.3

BIO.3.c

Positive Regulator Molecules

- [Narratore] Il ciclo
di una cellula è regolato

positivamente, promuovendo il
progresso attraverso le fasi

tramite l'interazione di due classi

di proteine trovate nel citoplasma:

cicline e chinasi dipendenti
dalla ciclina o CDK.

Per impostazione predefinita,
i CDK sono sempre presenti

in una cellula in forma inattiva.

Devono legarsi a una ciclina
specifica per essere attivati.

Quando questo complesso si forma,

il CDK può fosforillare
una proteina bersaglio,

che altera la sua funzione

e avvia la cellula nell'avanzamento
della fase successiva.

Nella maggior parte dei casi
quando una ciclina è degradata,

il CDK è inattivo,

segnalando la fine di
una particolare fase.

Ad esempio, durante G-one
quando un tipo di cclina,

chiamato D, è sintetizzato
e si lega a un CDK,

la cella passa alla fase S come

un' altro ciclina E, raggiunge
il picco e forma un complesso

con CDK per promuovere
la replicazione del DNA.

E viene quindi degradata
dagli enzimi citoplasmatici

e la concentrazione di ciclina A aumenta

durante la fase S e rimangono
alti in G-due per promuovere

l'ingresso nella fase M
quando in un complesso attivo.

Dopo che A viene degradato,
le concentrazioni di ciclina B

hanno il picco in fase M
e il complesso attiverà

le diverse fasi della mitosi.

Quando i livelli di B scendono,
la cellula esce dalla mitosi

e si divide.

Quindi, i livelli delle
quattro diverse cicline

variano in modelli prevedibili

e si combinano con CDK coerenti

in punti specifici per
raggiungere lo slancio in avanti.

Bai, Jingwen, Yaochen Li e Guojun Zhang. "Regolazione del ciclo cellulare e scoperta di farmaci antitumorali". Cancer Biology & Medicine 14, n. 4 (novembre 2017): 348-62. [<a href="https://doi.org/10.20892/j.issn.2095-3941.2017.0033" target="__blank">Sorgente</a>]

Laphanuwat, Phatthamon e Siwanon Jirawatnotai. "Ruoli immunomodulatori dei regolatori del ciclo cellulare". Frontiere nella biologia cellulare e dello sviluppo 7 (2019). [<a href="https://doi.org/10.3389/fcell.2019.00023" target="__blank">Sorgente</a>]

molecole regolatrici positive

Per produrre in modo coerente cellule sane, il ciclo cellulare, ovvero il processo che genera cellule figlie, deve essere regolato con precisione.

I punti di controllo regolatori interni assicurano che le dimensioni di una cellula, le riserve energetiche e la qualità e completezza del DNA siano sufficienti per avanzare attraverso il ciclo cellulare. A questi checkpoint, i regolatori positivi e negativi promuovono o inibiscono la continuazione di una cellula attraverso il ciclo cellulare.

I regolatori positivi includono due gruppi proteici che consentono alle cellule di passare attraverso i checkpoint normativi: cicline e cicline chinasi dipendenti (CCD). Queste proteine sono presenti negli eucarioti, che vanno dal lievito all'uomo.Le cicline possono essere classificate come cicline G1, G1/S, S o M in base alla fase del ciclo cellulare o alla transizione in cui sono più coinvolti. In generale, i livelli di una data ciclina sono bassi durante la maggior parte del ciclo cellulare, ma aumentano bruscamente al checkpoint a cui contribuiscono maggiormente (le cicline G1 sono un'eccezione, in quanto sono necessari per tutto il ciclo cellulare). La ciclina viene quindi degradata dagli enzimi nel citoplasma e i suoi livelli diminuiscono. Nel frattempo,le cicline necessarie per i prossimi checkpoint si accumulano.

Per regolare il ciclo cellulare, i ciclini devono essere legati a una ciclina chinasi dipendente (CDK), un tipo di enzima che lega un gruppo di fosfati per modificare l'attività di una proteina bersaglio. Il CDK è attivo solo quando è associato a una cicloina. A seconda della ciclina a cui sono vincolati, i CK sono indirizzati a diverse proteine bersaglio che sono necessarie per passare a una particolare fase del ciclo cellulare.

Rispetto alle cicline, i CDK rimangono a livelli relativamente costanti durante tutto il ciclo cellulare. Tuttavia, la loro attività e le proteine che prendono di mira cambiano in base a diversi livelli di cicline durante il ciclo cellulare.

Molecole regolatrici positive

To consistently produce healthy cells, the cell cycle&#8212;the process that generates daughter cells&#8212;must be precisely regulated.

Internal ...

Education

Didattica

JoVE Core

Biologia

Cellular Processes

Processi cellulari

Cell Cycle and Division

Ciclo e divisione cellulare

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

cyclins and cdks in the cell cycle

Cyclins and CDKs help control the cell cycle, the process that produces daughter cells. Cells use internal checkpoints to make sure their size, energy reserves, and DNA are ready before they move forward. At these checkpoints, positive regulators help the cell continue, while negative regulators slow or stop it.

The main positive regulators are cyclins and cyclin-dependent kinases, or CDKs. These proteins are found in eukaryotes, from yeast to humans. Cyclins are grouped by the stage they help control: G1, G1/S, S, or M cyclins. G1 cyclins are unusual because they are needed throughout the cell cycle.

Cyclin levels usually stay low for most of the cycle. They rise sharply at the checkpoint where they are needed most, then enzymes in the cytoplasm break them down and their levels fall. At the same time, the next cyclins begin to build up for later checkpoints.

CDKs are enzymes that add a phosphate group to a target protein. A CDK becomes active only when it is bound to a cyclin. The cyclin it binds helps direct the CDK to the right target proteins for that stage of the cell cycle. CDK levels stay fairly constant, but their activity changes as cyclin levels rise and fall.

Cyclins and CDKs in the Cell Cycle

what is the cell cycle?

Cell Cycle Checkpoints and Cancer

The cell cycle is the set of steps a eukaryotic cell follows as it grows and divides. In somatic cells, it has two main stages: interphase and the mitotic phase. During interphase, the cell grows, carries out its basic metabolic functions, copies its DNA, and gets ready for mitotic cell division. After interphase, the cell enters mitosis and cytokinesis. Mitosis divides the nuclear material, and cytokinesis divides the cytoplasm. These steps produce two daughter cells that are identical to the...

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binary fission

How Cells Split by Binary Fission

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genomic dna in eukaryotes

How Eukaryotic DNA Fits Inside the Nucleus

Eukaryotic DNA fits inside the nucleus by packing into a highly compact form. Eukaryotes have large genomes compared with prokaryotes, so their DNA must be tightly organized to fit inside one cell. The process starts when DNA wraps around proteins called histones. These DNA-histone units form nucleosomes, which are connected by linker DNA. The nucleosomes then coil into chromatin fibers, and additional fibrous proteins compact the chromatin even more. This packed material is called chromatin,...

interphase

Interphase in the Cell Growth Cycle

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mitosis and cytokinesis

Cell Cycle Stages in Mitosis

Cell cycle stages in mitosis show how a eukaryotic cell copies its DNA and then divides into two daughter cells. The cycle is controlled by regulatory systems and by outside signals that affect cell growth and division. In typical human cells, the full cycle takes about 24 hours and includes two major phases. The first is DNA replication during the S phase of interphase. The second is the mitotic, or M, phase, which includes mitosis and cytokinesis. G1 and G2 are the gap stages between these...

positive regulator molecules

Cyclins and CDKs help control the cell cycle, the process that produces daughter cells. Cells use internal checkpoints to make sure their size, energy reserves, and DNA are ready before they move forward. At these checkpoints, positive regulators help the cell continue, while negative regulators slow or stop it. The main positive regulators are cyclins and cyclin-dependent kinases, or CDKs. These proteins are found in eukaryotes, from yeast to humans. Cyclins are grouped by the stage they help...

negative regulator molecules

Cell Cycle Stop Signals: p53, p21, and Rb

Cell cycle stop signals help control when a cell can move forward through division. Negative regulators pause or end the cell cycle until the cell meets the right conditions. Three well-studied negative regulators are p53, p21, and retinoblastoma protein, or Rb. Their roles became clear after faulty versions were found in cancer cells that kept replicating uncontrollably. These proteins act mostly at the G1 checkpoint, which comes early in the cell cycle. P53 has a strong effect on whether a...

cancer

Cancer Treatment, Personalization, and Cell Growth

Cancer develops when mutations affect genes that control cell division. Those changes can remove the normal brakes on growth and lead to uncontrolled cell proliferation. Modern science and medicine have improved how cancer is understood and treated, and some patients can now be cured. There is still no single cure for cancer because cancer is not one disease. It is a large group of many diseases. Even when two people have the same mutation in an oncogene or a tumor suppressor gene, their...

key terms and concepts

Learn how cyclins and CDKs regulate cell cycle checkpoints, with cyclin types, changing levels, and how CDKs are activated to move cells forward.

Cyclins and CDKs in the Cell Cycle | JoVE K12

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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

Texas Essential Knowledge and Skills

BIO.6

BIO.6.A

new-york-state-science-learning-standards

New York State Science Learning Standards

Inheritance and Variation of Traits

HS-LS1-4.

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9-12

SB1.b

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BIO.3.e

Cyclins and CDKs in the Cell Cycle

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