overview of the cell cycle

cell cycle : A cell reproduces by performing an orderly sequence of events in which it duplicates its contents and then divides in two. (Cycle of duplication and division)

The most fundamental task in one cell cycle: the passing on of its genetic information to the next generation of cells

The duration of the cell cycle varies greatly from one cell type to another.
不同细胞的细胞周期时长差异巨大

M-phase里分为mitosis和cytokineses
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如果环境不适应,细胞可以停在G1期或进入G0期,环境合适时候会通过start/resriction point,开始DNA复制
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研究细胞周期的方法

Observe living cells with a microscope
Staining cells with special dyes or with antibodies that recognize specific cell components
给细胞染色,比如DNA染色,微管染色
Analysis of DNA content by the use of DNA-binding dye (Hoechst 33342)and a
flow cytometer

the cell cycle control system

The Cell-Cycle Control System Triggers the Major Events of the Cell Cycle

cell-cycle contron system 基于一系列的 biochemical switches,每个开关触发一个细胞周期中的事件

In most eukaryotic cells, the cell-cycle control system governs管理 cell-cycle progression at three major regulatory transitions过渡

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Cdks

The Cell-Cycle Control System Depends on Cyclically Activated Cyclin-Dependent Protein Kinases (Cdks)
周期蛋白依赖性蛋白激酶

cdks结合cyclins周期蛋白,形成复合体,然后催化细胞周期中的关键事件
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cyclins

The most important Cdk regulators.

Bounding tightly to a cyclin is a prerequisite先决条件 of the activation of Cdks.

Cyclins undergo a cycle of synthesis and degradation in each cell cycle.

不同周期蛋白含量的变化会导致不同的周期蛋白去结合cdks

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图中的三种cyclins是所有真核细胞必须的,还有一种是G1-cyclin

cdk被激活的结构图👇

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抑制cdk

通过inhibitory phosphorylation抑制👇
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通过cdk inhibitor protein(CKIs)抑制👇
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Metaphase to Anaphase分裂中期到分裂后期

这部分估计不考

Regulated Proteolysis蛋白水解 Triggers the Metaphase-to-Anaphase Transition

Progression through the metaphase- to-anaphase transition is triggered by protein destruction

APC/C 催化加速cdk-M-cyclin水解👇
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APC/C 激活separase,separase催化姐妹染色单体分开👇
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还有一种东西叫SCF,在G1后期专门泛素化CKI促进降解,帮助激活S-cdk并开始DNA复制
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总结

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S phase

复制一次

G1会形成preRC,授权复制起点,到了S期会激活DNA解旋酶,复制一次之后的复制起点没有preRC,没有被授权,这样就控制了S期DNA只复制一次👇
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姐妹单体不分开

Sister-chromatid cohesion depends on a large protein complex called cohesion.
姐妹染色单体的黏连依赖于一种称为黏连蛋白的大型蛋白质复合体

在S期DNA复制时，黏连蛋白会在每条姐妹染色单体的长度上多个位置沉积

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mitosis

prophase, prometaphase, metaphase, anaphase, and telophase
前期、前中期、中期、后期和末期

主要分成两部分

M-cdk trigger G2/M transition,发生前期,前中期和中期的过程
APC/C trigger metaphase-to-anaphase transition,发生中期到后期的过程

M-cdk突增👇
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原理是正反馈调节👇

prophase前期

1.形成染色体

Condensin Helps Configure Duplicated Chromosomes for Separation
凝缩蛋白帮助配置复制的染色体以进行分离

细胞在早期有丝分裂中投入大量能量，逐渐将姐妹染色单体重新组织成相对较短、独特的结构,以便在后期更容易被拉开

chromosome condensation : the chromatids are dramatically compacted
sister-chromatid resolution : the two sisters are resolved into distinct, separable units

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