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

- [나레이터] 세포의 순환주기는 분명하게 정해져 있는데,이는 세포질에서 발견되는 두 종류 단백질의상호작용을 통한 단계들을 거쳐서진행되는 과정으로,이 두 종류의 단백질은 각각 사이클린과 사이클린 의존 단백질 인산화효소(CDK)입니다.자연스럽게, CDK는 언제나 비활성화된 형태로세포 안에 존재하고 있습니다.CDK는 활성화 되기 위해서 반드시 특정한 사이클린과 결합되어야 합니다.이러한 결합체가 만들어질 때,CDK는 목표 단백질을 인산화할 수 있게 되는데,이는 해당 단백질의 기능을 바꾸고세포가 다음 단계로 나아갈 수 있도록 만듭니다.대부분의 경우 사이클린이 분해되면,CDK는 비활성화 되는데,이는 특정한 단계의 종료를 알리는 신호가 됩니다.예를 들어, D라는 이름의 사이클린은 G1 단계에서CDK와 결합해서 화합하는데세포는 이에 따라 S-단계로 돌입하게 되고이에따라 사이클린 E가 CDK와 결합해DNA 복제를 촉진하게 됩니다.그리고나서 E는 세포질의 효소에 의해 분해되고S-단계가 진행되는 동안 사이클린 A의 농도가 짙어지는데사이클린 A 결합체는 G2단계에서도 짙은 농도를 유지하면서이 결합체가 활성화되어 있는 동안 세포가 M-단계로 진입하도록 촉진합니다.사이클린 A가 분해되고 나면, 사이클린 B의 농도가M-단계에서 절정에 이르고 사이클린 B 결합체는 체세포 분열의또 다른 단계로 이끕니다.사이클린 B의 농도가 떨어지면, 세포는 체세포 분열을 끝내고 나뉘어집니다.이와 같이, 4가지 종류의 사이클린 농도는여러 예측가능한 패턴을 가지고 있고다음 단계로 나아가는 계기를 만들기 위해 각 특정 시점에일관된 CDK와 결합합니다.

Bai, Jingwen, Yaochen Li, and Guojun Zhang. "Cell Cycle Regulation and Anticancer Drug Discovery." Cancer Biology & Medicine 14, no. 4 (November 2017): 348–62. [<a href="https://doi.org/10.20892/j.issn.2095-3941.2017.0033" target="__blank">소스</a>]

Laphanuwat, Phatthamon 및 Siwanon Jirawatnotai. "세포주기 조절자의 면역 조절 역할." 세포 및 발달 생물학의 프론티어 7 (2019). [<a href="https://doi.org/10.3389/fcell.2019.00023" target="__blank">소스</a>]

양성 조절 분자

건강한 세포를 지속해서 생산하기 위해서는 딸세포(daughter cell)를 생성하는 과정인 세포주기가 정확하게 조절되어야 합니다.
 
 내부 조절 확인지점(internal regulatory checkpoint)은 세포의 크기, 에너지 저장량, DNA의 질과 완전성이 세포주기를 진행하기에 충분하다는 것을 확인합니다. 이러한 확인지점에서 양성 조절자(positive regulator)와 음성 조절자(negative regulator)는 세포가 세포주기를 따르는 것을 촉진하거나 억제합니다.
 
 양성 조절자에는 세포가 조절 확인지점을 통과할 수 있도록 만드는 두 가지 단백질 그룹, 즉 사이클린(cyclin)과 사이클린 의존성 인산화효소(cyclin-dependent kinase, CDK)가 포함됩니다. 이 단백질은 효모에서 인간에 이르는 진핵생물에 존재합니다.
 
 사이클린은 세포주기 단계 또는 가장 많이 관여하는 전환(transition)을 기준으로 G1, G1/S, S, 또는 M 사이클린으로 분류할 수 있습니다. 일반적으로 사이클린의 농도는 대부분의 세포주기 동안 낮지만 가장 많이 기여하는 확인지점에서 갑자기 증가합니다(세포주기 전체에 필요한 G1 사이클린은 예외). 그 뒤 사이클린은 세포질(cytoplasm) 내 효소에 의해 분해되고 농도는 감소합니다. 한편, 다음 확인지점에 필요한 사이클린이 축적됩니다.
 
 사이클린은 세포주기를 조절하기 위해 사이클린 의존성 인산화 효소(CDK)에 결합해야 합니다. CDK는 인산기(phosphate group)를 부착하여 표적 단백질의 활동을 조절하는데, 사이클린이 결합한 경우에만 활성화합니다. CDK는 결합한 사이클린에 따라 특정한 세포주기 단계로 넘어가는 데 필요한 다양한 표적 단백질로 향합니다.
 
 사이클린에 비해 CDK는 세포주기 내내 비교적 일정한 수준을 유지합니다. 하지만, CDK의 활동과 CDK의 표적 단백질은 세포주기에 걸쳐 다양한 농도의 사이클린에 따라 변합니다.

건강한 세포를 지속적으로 생산하기 위해서는 딸세포를 생성하는 과정인 세포주기를 정밀하게 조절해야 합니다.

내부...

Education

교육

JoVE Core

생물학

Cellular Processes

세포 과정

Cell Cycle and Division

세포 주기와 분열

KEY TERMS AND CONCEPTS

주요 용어 및 개념

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...

genomic dna in prokaryotes

Prokaryote Chromosomes and Plasmids

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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

Interphase is the stage of the cell cycle when a eukaryotic cell grows and copies its DNA before mitosis. In a typical human cell, the full cell cycle takes about 24 hours, and interphase makes up about 95 percent of that time. It is followed by mitosis, also called M, when the cell divides. After mitosis and cytokinesis, cells enter the G1 phase, or gap 1. During G1, cells grow continuously and prepare for DNA replication. They are metabolically active and copy essential organelles and...

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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Cyclins and CDKs in the Cell Cycle

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