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

يتم تنظيم دورة الخلايا بشكل إيجابي تعزيز التقدم من خلال المراحل عبر تفاعل فئتين من البروتينات وجدت في السيتوبلازم. السيكلينات والكينازات المعتمدة على السيكلين،أو CDK. بشكل افتراضي،تكون CDKs موجودة دائمًا في خلية في شكل غير نشط.يجب أن ترتبط مع سيكلين معين ليتم تفعيلها. عندما يتشكل هذا المركب،يمكن لـ CDK أن يفسف البروتين المستهدف الذي يغير من وظيفته ويبدأ الخلية للتقدم إلى المرحلة التالية. في معظم الحالات،عندما يتحلل cyclin،CDK غير نشط،مما يشير إلى النهاية من مرحلة معينة.مثلاًخلال G1،عندما يكون هناك نوع واحد من cyclin،يدعى D،يتم توليفها ويرتبط CDK،التحولات الخلية في المرحلة S،كما cyclin آخر،E،قمم ويشكل مجمع مع CDK لتعزيز تكرار الحمض النووي. ثم يتحلل E بواسطة إنزيمات السيتوبلازم ويزداد تركيز السيكلين أ طوال مرحلة S وتبقى عالية في G2 لتعزيز الدخول في المرحلة M عندما تكون في مجمع نشط. بعد التدهور A،تركيزات cyclin B الذروة في المرحلة M والمجمع سوف تنشط مراحل مختلفة من الانقسام.عندما تنخفض مستويات B،تخرج الخلية من الانقسام وتنقسم. وبالتالي،تختلف مستويات الإعصارات الأربعة المختلفة في أنماط يمكن التنبؤ بها والجمع بين CDKs متسقة في نقاط محددة لتحقيق الزخم إلى الأمام.

باي ، جينغوين ، ياوشين لي ، وغوجون تشانغ. "تنظيم دورة الخلية واكتشاف الأدوية المضادة للسرطان". بيولوجيا السرطان والطب 14 ، العدد 4 (نوفمبر 2017): 348-62. [<a href = "https://doi.org/10.20892/j.issn.2095-3941.2017.0033" target = "__blank" >المصدر</a>]

لافانوات ، فاثامون ، وسيوانون جيراواتنوتاي. "الأدوار المناعية لمنظمات دورة الخلية". الحدود في علم الأحياء الخلوي والتنموي 7 (2019). [<a href = "https://doi.org/10.3389/fcell.2019.00023" target = "__blank" >مصدر</a>]

جزيئات المنظم الموجب

لإنتاج خلايا سليمة باستمرار ، يجب تنظيم دورة الخلية _ العملية التي تولد الخلايا الوليدة _ بدقة.

تضمن نقاط التفتيش التنظيمية الداخلية أن حجم الخلية واحتياطيات الطاقة وجودة الحمض النووي واكتماله كافية للتقدم خلال دورة الخلية. في نقاط التفتيش هذه ، تقوم المنظمين الموجبين والسالبين بتعزيز أو منع استمرار الخلية خلال دورة الخلية.

تشمل المنظمات الإيجابية مجموعتين من البروتين تسمح للخلايا بالمرور عبر نقاط التفتيش التنظيمية: الأعاصير والكينازات المعتمدة على السيكلن (CDKs). توجد هذه البروتينات في حقيقيات النوى ، وتتراوح من الخميرة إلى البشر.

يمكن تصنيف السيكلينات على أنها G1 ، G1/ S ، S ، أو سيكلينات (M) استناداً إلى مرحلة دورة الخلية أو الانتقال الأكثر مشاركة فيها. بشكل عام ، مستويات يكون سيكلين معيناً منخفضاً خلال معظم دورة الخلية ولكنه يزداد بشكل مفاجئ عند نقطة التفتيش التي يساهم فيها بشكل كبير (سيكلينات G1 هي استثناء ، لأنها مطلوبة طوال دورة الخلية). ثم يتحلل السيكلين بواسطة الإنزيمات الموجودة في السيتوبلازم وتنخفض مستوياته. في غضون ذلك ، تتراكم السيكلينات اللازمة لنقاط التفتيش التالية.

لتنظيم دورة الخلية ، يجب الارتباط بين السكلين و كيناز يعتمد على سيكلين (CDK)_ وهو نوع من الإنزيم الذي يربط مجموعة الفوسفات لتعديل نشاط البروتين المستهدف. يكون كيناز المعتمد على سيكلين نشطاً فقط عندما يكون مرتبطاً بسيكلين. اعتماداً على السيكلين التي يرتبطون بها ، يتم توجيه الكيناز المعتمد على سيكلين إلى بروتينات مستهدفة مختلفة مطلوبة للتقدم إلى مرحلة دورة خلية معينة.

بالمقارنة مع السيكلينات ، تظل الكينازات المعتمدة على سيكلين عند مستويات ثابتة نسبياً طوال دورة الخلية. ومع ذلك ، فإن نشاطهم والبروتينات التي يستهدفونها يتغيرون وفقاً لمستويات مختلفة من الأعاصير عبر دورة الخلية
.

لإنتاج خلايا سليمة باستمرار ، يجب تنظيم دورة الخلية - العملية التي تولد الخلايا الوليدة - بدقة.

داخلي...

Education

JoVE Core

علم الأحياء

Cellular Processes

العمليات الخلوية

Cell Cycle and Division

دورة الخلية وانقسامها

KEY TERMS AND CONCEPTS

المصطلحات والمفاهيم الأساسية

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

Binary fission is a common way that bacteria and archaea reproduce. In this process, one parent cell divides into two parts. Each new cell can then grow to the size of the original parent cell. This is an asexual form of reproduction, so the cells produced are genetically identical. Binary fission can happen very fast. In the time it takes one bacterial cell to divide, the number of cells in the culture doubles. That time is called the doubling time. Escherichia coli cells often divide every...

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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biology

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.

Georgia Standards of Excellence

9-12

SB1.b

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BIO.3.e

Cyclins and CDKs in the Cell Cycle

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