7 第11章 RNA的生物合成

primer
Enzyme product base pair
yes
DNA polymerase dsDNA A-T, G-C
no
RNA polymerase ssRNA A-U, T-A, G-C
目录
The processes of gene expression are different in prokaryotes and eukaryotes.
The sequence of ribonucleotides in an RNA molecules is complementary to the sequence in one strand of DNA.
Asymmetric transcription （不对称转录）: Coding strand
目录
5' 3'
GCAGTACATGTC CGTCATGTACAG
3' coding 5'
strand template strand
transcription
5' GCAGUACAUGUC 3' RNA
translation N-------- Ala· Val· His· Val-------C peptide
目录
Similarity between replication and transcription
Both processes use DNA as the template. Phosphodiester bonds are formed in both cases.
Both synthesis directions are from 5´ to 3´.
DNA regions that can be transcribed into RNA are called structural genes (结构基因).
A B C D
目录

Only one of the two DNA strands serves as a template for RNA synthesis
molecules using DNA strands as a templates（模
板） is referred to as transcription.
The genetic information can be transferred from DNA to RNA.
Transcription
目录
The prokaryotic（原核） RNA polymerase is a multiple-subunit protein of ~480kD. RNA polymerase does not require a primer (引物） to initiate synthesis. RNA polymerase initiate RNA synthesis by binding a special DNA sequence —— promoter（启动子）.
gene expression in stationary phase cells expression of flagellar operons involved in heat shock and oxidative stress responses; regulates expression of extracytoplasmic proteins regulates the fec genes for iron dicitrate transport
σFecI
§ 1.3 The initiation of transcription involves the binding RNA polymerase to promoter
转录是不连续、分区段进行的。
每一转录区段可视为一个转录单位，称为操纵子(operon)。 Operon includes multiple structural genes and relative upstream(上游） regulatory sequences.
Catalyze polymerization (催化作用, Rifampicin 利福平(-)) Bind & open DNA template (结合模板) Recognize the promoter for synthesis initiation （识别启动子）



70263
In prokaryotic cells, all 3 RNA classes are synthesized by a single polymerase.
第十一章
Chapter 11
RNA的生物合成
RNA Biosynthesis
目录
The Central Dogma
Gene expression replication replication translation transcription
Reverse transcription
目录

In the biosphere, there are two ways of synthesis of RNA : One is transcription（转录）, DNA-dependent RNA synthesis， catalyzed by DNA-dependent RNA polymerase Another is RNA replication, RNA-dependent RNA synthesis, catalyzed by RNA-dependent RNA polymerase，Commonly found in RNA viruses other than retroviruses (逆转录病毒）
Seven alternative sigma factors of E. coli.
sigma factor σ70 σ54 function principal sigma factor nitrogen-regulated gene transcription
σ32
σS σF σE
heat-shock gene transcription
DNA
RNA
目录
Materials involved in transcription：
substrates: NTP (ATP, UTP, GTP, CTP) template: DNA ( but only one strand） enzyme: RNA polymerase, RNA-pol Other protein：Rho factor(ρ), transcriptional factors
目录
The subunits of E. coli RNA pol and their functions
subunit MW
36512
150618 155613
function
Determine the DNA to be transcribed（决定哪些基因 被转录，与调控蛋白相互作用，控制转录速率)
(+) RNA 5'●-pUUNNNNN……………………NNNAAAAAAAn 3' synthesis of（-）RNA ←UUp-●
(-) RNA 3'AANNNNNNN……………………NNNUUUUUUUp-● 5' ●-pUU→ synthesis of （+）RNA
目录
转录 (transcription) ： The synthesis of RNA
The template strand (模板链）is the strand from which the RNA is actually transcribed.
The coding strand（编码链） is the strand whose base sequence specifies the amino acid sequence of the encoded protein.
5 3
Template strand
3 5
Template strand
Coding strand Structural gene
What does Asymmetric transcription（不 对称转录） mean?
In the two strands of a structural gene, just one strand is used as the template of transcription;（在DNA分子双链上，一股链用作 模板指引转录，另一股链不转录） In the case of a double-stranded DNA molecules many genes, the template strand for each gene will not necessarily be the same strand of the DNA double helix. （ 模板 链并非总是在同一单链上）
Obey base pairing rules
目录
Differences between replication and transcription
replication template substrate double strands dNTP transcription single strand NTP
目录
§ 1.2.2 bacterial RNA polymerase is a multisubunits （亚基）enzyme Holoenzyme（全酶） core enzyme（核心酶）