Part V: How genes are regulated
Chapter 15:
Gene Regulation in Prokaryotes
Chapter 16:
Gene Regulation in Eukaryotes
Chapter 15:
Gene Regulation in
Prokaryotes
Gene activity is regulated
primarily at the level of
transcription
lactose operon (lac operon)
Structure of lactose operon
The action of CAP-cAMP
complex in lac operon
CAP ( catabolic gene
activator protein) structure
cAMP and CAP (catabolite activator protein)
cAMP（饥饿信号）
细菌
与分解物基因激活物结
合的蛋白 （catabolite
gene activator
protein,CAP）
发挥作用
哺乳类动物
激活PK
导致细胞内一系
列酶活性的改变
The general condition of
regulation of gene expression
in prokaryotes
•the change of environment
•positive regulation & negative
regulation
negative regulation
repressor of lac bind to
operator
Positive regulation
CAP-cAMP complex
trytophan operon (Trp operon )
a. Structure
mechanism of regulation
*negative regulation of repressor
the structure of repressor attenuation
Attenuator
located in L gene,contains a ρ
independent termination structure
# the mechanism of attenuation
大肠杆菌
低Trp培养基
转录生成6720
个AA的全长多
顺反子mRNA
高Trp培养基
转录终止于L基
因5’端140个AA
• These recognize only certain promoters and
thus allow transcription of a select category of
genes. Other global signals include cold and
heat shock proteins that function to help the
cell overcome temperature stress.
Small RNAs (sRNA)
---Regulation of translation initiation and transcription termination
by altering the accessibility of RBS and the formation of
terminator, respectively.
---Regulation by base pairing with the targeted sequences on
mRNAs。
---Acts in trans similar to miRNA, but does not require specific
machinery for action.
53
Riboswitches are regulatory RNA elements that
act as direct sensors of small molecule
metabolites to control gene transcription or
translation.
---Regulate translation initiation and transcription
termination by altering the accessibility of RBS and the
formation of terminator, respectively.
---Reside upstream of the targeted mRNA, and form
specific structure to bind its small molecule ligand.
---Act in cis by alteration of its own structure upon the
binding of the small metabolites.
The structure of a riboswitch in its regulated
mRNA
55
Control of transcription
termination by a riboswitch
代谢物
代谢物
Control of translation
initiation by a
riboswitch.
56
Alteration of of the structure of the
SAM riboswitch upon the binding of
SAM (S-adenosyl methionine)
57
The 2nd structures of 7 riboswitches
and metabolites that they sense
58
Chapter 16: Gene
Regulation in Eukaryotes
(1) character of regulation
(2) activation of chromatin
cis- acting elements & trans –
acting factors involved in gene
regulation
a. cis-acting elements
* concept
* type
Promoter & proximal upstream
sequences
according to its function of affecting to
RNA pol
far from the transcription site： two kinds
(-CAAT- ,GC box)
near the transcription site
(TATA box)
inhancer
concept
character
response elaments
concept
character
trans – acting factors
* concept
* structure
bind to cis-element
two domain
activity domain
* the mechanism of its functure
* modles of trans-acting factors
# helix-turn helix
structure
helix---turn---helix
(7-9A.A)
(7-9A.A)
zinc-fingers
structure
character
leucine –zipper
structure
character
# helix-loop-helix
structure
* The character & rule of
trans-acting factors’ function