called repressed expression（阻遏表达）
（enzymes which catalyze Trp synthesis）.
在一定机制控制下，功能上相关的一组基
因，无论其为何种表达方式，均需协调一
致、共同表达，即为协调表达 (coordinate expression) ， 这 种 调 节 称 为 协 调 调 节 (coordinate regulation)。
Operator(操纵序列）——switch
The DNA sequence adjacent to the structural genes that the repressor protein can bind to and prevent the transcription of structural genes.
a.
Special DNA sequences
b.
c.
Regulatory proteins
DNA-protein interaction and protein-protein interaction RNA polymerase
d.
a. Special DNA sequence
（1）For prokaryotic systems: Operon（操纵子） is composed of structural genes, promoter, operator, and other regulatory sequences. Promoter Other regulatory sequence
Gene Expression Regulation( 基因表达调控 ) ：
在同一机体的各种细胞内含有相同的遗传信
息，即相同的结构基因，它们在各种细胞中并非同
时表达，而是根据机体生长、发育、繁殖的需要， 随着环境的变化，有规律的选择性、程序性、适度 地表达，以适应环境，发挥其生理功能。这就是所 谓的调控，即基因表达的调节和控制（ regulation

第二节
基因表达调控的基本原理
Basic Principles of Gene Expression Regulation
§2.1 Regulatory Elements

Gene expression is a multiple-level and very complicated process. Transcription initiation is a key point of controlling gene expression.
For example:

By switching genes off when they are not needed, cells can prevent resources from being wasted. There should be natural selection favoring the ability to switch genes on and off（基因开和关）.（alcohol ——ADH） Cancer（肿瘤） results from genes that do not turn off properly. Cancer cells have lost their ability to regulate mitosis, resulting in uncontrolled cell division.
DNA B A mRNA DNA A mRNA
start
RNA pol Ⅱ
start
RNA polⅡ
Coding sequence
B
Cis-acting elment
Structure gene
-GCGC---CAAT---TATA
Initiation site
enhancer
TATA box
CAAT box
Sturctural genes
Operator
Promoter 启动子
The DNA sequence that RNA-pol can bind to and initiate the transcription，determine transcription direction, template and activity（决定转录方向、模 板和活性）. RNA polymerase binds to different promoters with different efficiency.

1.3 Type of gene expression a. Constitutive expression(组成性表达)
Some genes are essential and necessary for life, and therefore are continuously expressed(持续表达), such as those enzymes involved in TAC. These genes are called housekeeping genes(管家基因). Internal reference sample(内参)of RT-PCR： β -actin，GAPDH
第十三章 charpter 13
基因表达调控
Regulation of Gene Expression
General concept
Gene
expression is regulated. adapt to environmental change of gene expression generally
b. Induction（诱导）
and repression （阻遏）
The expression levels of some genes fluctuate （波动）in response to the external signals.
Some genes（Inducible gene，可诱导基因） demonstrate higher expression level once
can be positive or negative.
contents

Basic concepts and principles

Regulation of gene expression in prokaryotes
Regulation of gene expression in prokaryotes
CAP
I
RNA P pol
O
Z
Y
A
ntrC蛋白结合的DNA元件是细菌DNA中的一种增强子。
（2）For eukaryotic systems:
Cis-acting elements is the special DNA sequence that can affect the expression of its own gene.

第一节 基因表达调控的基本概念
Basic concepts of Gene Expression Regulation
§1.1 Conceptsห้องสมุดไป่ตู้
Gene(基因): A DNA segment that contains the all genetic information required to encodes RNA and protein molecules. Genome(基因组): A complete set of genes of a given species. (22+XY+mtDNA) Gene expression(基因表达): A process of gene transcription and translation.
1.2 Specificity of gene expression

Temporal specificity (also called stage specificity): why in the infant not in the aged ones? (甲胎蛋白AFP） Spatial specificity (also called tissue specificity): why in liver not in brain? （白蛋白）
Transcription factor CREB Estrogen receptor Glucocorticoid receptor Heat shock factor Serum response factor Consensus sequence TGACGTCA AGGTCANNNTGACCT AGAACANNNTGTTCT GAANNTTCNNGAA CC(A/T)6GG
being activated. It is called induced expression
（诱导表达）（Hsp gene）. On the other hand, some genes （repressible gene，可阻遏基因）are repressed and their expression levels are lower. It is
Response element CRE ERE GRE HSE SRE
b. Regulatory proteins
（1）For prokaryotic systems:
• Specificity factors alter the specificity of RNA polymerase for a given promoter or a set of promoters • Repressors bind to the operator and prevent the transcription, known as negative regulation.