Lecture 10

Lecture 10 Chapter 4 Transcription in Eukaryotes 4.1 Eukaryotic RNA polymerases 4.2 Eukaryotic Promoters 4.3 General Transcription Factors and Initiation 4.4 Specific Transcription Factors and Transcriptional Regulation 4.5 Structures of specific transcription factors 4.6 Experiments 第4章真核生物转录 4.1 真核生物RNA聚合酶 4.2 真核生物启动子 4.3 通用转录因子与转录起始 4.4 特异转录因子与转录调控 4.5 特异转录因子的结构 4.6 实验研究

Review of Lecture 9 A1→ 4.1 Eukaryotic RNA polymerases 真核生物RNA聚合酶 A2→ 4.2 Eukaryotic Promoters真核生物启动子 A3→ 4.3 General Transcription Factors and Initiation 通用转录因子与转录起始

A1→ 4.1 Eukaryotic RNA polymerases 真核生物RNA聚合酶 Table 4.1 Eukaryotic RNA polymerases and their roles 表4.1 真核生物RNA聚合酶和它们的作用

A2→ 4.2 Eukaryotic Promoters真核生物启动子 Promoter of eukaryotic RNA polymerase II 真核生物RNA聚合酶II的启动子

A3→ 4.3 General Transcription Factors and Initiation（通用转录因子与转录起始） Eukaryotic RNA polymerase II: “I need help from other proteins.” Pre-initiation complex 前起始复合体

Questions for Lecture 10 Q1→ What proteins are needed to help RNA polymerases I and III to initiate transcription?RNA聚合酶I和III需要哪些蛋白帮助来起始转录？ Q2→ What are the two types of specific transcription factors? How can they affect initiation of transcription? 特异转录因子分哪两种类型？它们是如何影响转录起始的？ Q3→ What are enhancers ? What are silencers ? 什么是增强子？什么是沉默子? Q4→ What kind of DNA-binding motif do prokaryotic proteins have? 原核生物具有什么样的DNA结合基序?

Vocabulary of Lecture 10 (1/2) activator repressor tighten loosen nucleosome enhancer silencer recruit 激活蛋白阻遏蛋白使…紧密使…松开核小体增强子沉默子召集

Vocabulary of Lecture 10 (2/2) domain motif helix-turn-helix recognition helix sea urchin accessible block ▪▪▪域基序（基本序列）螺旋-转角-螺旋（HTH）识别螺旋海胆可接近的阻断（通道）

Q1→ What proteins are needed to help RNA polymerases I and III to initiate transcription?RNA聚合酶I和III需要哪些蛋白帮助来起始转录？ RNA polymerase I RNA polymerase II RNA polymerase III Prokaryotic RNA polymerase

A1→ 4.3.3 General Transcription factors for RNA Polymerase I and IIIRNA聚合酶 I 和III的通用转录因子

A1-1→ General TFs of RNA polymerase I RNA 聚合酶I的通用转录因子 SL1结合到核心元件上并帮助召集RNA聚合酶I到启动子位置。UBF结合到上游启动子元件帮助SL1结合到核心元件上。

A1-2a→ General TFs of RNA polymerase III TFIIIC 帮助TFIIIB 结合到靠近转录起始位点的DNA上

A1-2b→ General TFs of RNA polymerase III TF IIIB 又帮助RNA聚合酶 III结合到该基因上

4.4 Specific Transcription Factors and Transcriptional Regulation特异转录因子与转录调控 Specific transcription factor 真核生物采用特异转录因子的蛋白质来改变转录速率

Specific transcription factors特异性转录因子 特异性转录因子：改变目标基因转录速率的的真核生物因子。 Specific transcription factors:Eukaryotic factors that change the rate of transcription of target genes. Factors（因子） Proteins（蛋白质） Elements（元件） DNA segments（DNA区段）

Q2→ What are the two types of specific transcription factors? How can they affect initiation of transcription?特异转录因子分哪两种类型？它们是如何影响转录起始的？ Specific transcription factor General transcription factors General transcription factors

A2→ The two types of specific transcrip-tion factors are activators and repressors 两类特异转录因子是激活蛋白和阻遏蛋白 4.4.1 Activators / 激活蛋白 4.4.2 Repressors / 阻遏蛋白

A2-1→ 4.4.1 Activators / 激活蛋白 能提高转录速率的特异转录因子称为激活蛋白。 Specific transcription factors that enhance the rate of transcription are called activators. • Help recruit the pre-initiation complex. • Help organize the subunits of the pre-initiation complex, and maintain cohesion of the complex. • Attract enzymes to loosen DNA from proteins, freeing important regions like the promoter.

1. Help recruit the pre-initiation complex 激活蛋白能帮助召集前起始复合体 Here, TFIID helps initiate transcription. Is it also called an activator ?

2. Help organize the subunits of the pre-initiation complex 激活蛋白能帮助组织前起始复合体的亚基并保持复合体的结合力

3. Attract enzymes to loosen DNA 激活蛋白能够吸引酶来从蛋白上松开DNA，让启动子这样的重要区域游离出来。

A2-2→ 4.4.2 Repressors / 阻遏蛋白 能阻碍基因转录的特异转录因子称为阻遏蛋白。 Specific transcription factors that prevent the transcription of a gene are called repressors. • Blocking the activity of activators. • Blocking access of the pre-initiation complex to the promoter. • Recruiting enzymes that tighten DNA around proteins.

1. Blocking the activity of activators 阻遏蛋白能阻碍激活蛋白的活性

2. Blocking access of the pre-initiation complex to the promoter. 阻遏蛋白能通过阻止前起始复合体接近启动子

3. Recruiting enzymes that tighten DNA around proteins 阻遏蛋白能召集酶使DNA紧密地缠绕在蛋白上

Q3→ What are enhancers ? What are silencers ? 什么是增强子？什么是沉默子? Silencer / 消音器 Warm up ?

4.4.3 Enhancers and Silencers增强子和沉默子 特异转录因子依靠DNA序列来告诉它们应该怎样调控每一种基因。这些序列称为增强子或沉默子，分别依赖于它们结合的是激活蛋白还是阻遏蛋白。 Specific transcription factors rely on DNA sequences to tell them how each gene should be regulated. These sequences are called enhancers or silencers, depending whether they bind activators or repressors, respectively.

A3-1→ Enhancers / 增强子 Enhancers: Regulatory DNA elements to which activators bind to enhance the rate of transcription. 增强子：具有调控作用的DNA元件，激活蛋白结合上去后可以增强转录速率。 Transcription is activated Activator Enhancer

A3-2→ Silencers / 沉默子 Silencers: Regulatory DNA elements that bind to repressors and cause repression of transcription. 沉默子：具有调控作用的DNA元件，阻遏蛋白结合上去后可以减弱转录速率。 Transcription is repressed Repressor Silencer

DNA looping / DNA成环 DNA会弯过来，这样这些距离远的调控区域就可以来到启动子的附近。

Sea Urchin Endo 16 gene 海胆中的Endo 16基因在启动子上游含有六个起调控作用的增强子和沉默子，它们能够响应十几种不同蛋白的调控作用。 A red sea urchin 红海胆

4.5 Structures of Specific Transcription Factors4.5 特异转录因子的结构 ? Eukaryotic Prokaryotic ?

Major Groove vs. Minor Groove Major groove A ≠ T G≠ C Minor groove A ≈ T G ≈ C 绝大多数识别特异序列的DNA结合蛋白都结合到DNA的大沟上

Q4→ What kind of DNA-binding motif do prokaryotic proteins have? 原核生物具有什么样的DNA结合基序? E. coli (Prokaryotic cells) 大肠杆菌(原核细胞)

A4→ 4.5.1 DNA-Binding Motifs in Prokaryotes 原核生物DNA结合基序 Helix-turn-helix: A common DNA-binding motif in prokaryotic proteins. Consists of two α-helices connected by a short peptide turn. 螺旋-转角-螺旋：原核生物中常见的DNA结合基序。由两个α-螺旋通过一个肽转角连接在一起。 The helix-turn-helix (HTH) motif Recognition helix

Negative Regulation – the lac Repressor负调控──lac阻遏蛋白

Show 3D structure of the lac repressor File: lac repressor with DNA.val

The trp repressor trp阻遏蛋白只有在存在色氨酸的情况下才能结合到DNA上

The trp repressor Operator DNA Trp E. coli Trp repressor

Show 3D structure of the trp repressor File: trp repressor.val

Essentials of Lecture 10 / 第10讲要点 A1→ 4.3.3 General Transcription factors for RNA Polymerase I and IIIRNA聚合酶 I 和III的通用转录因子 A2→ The two types of specific transcrip-tion factors are activators and repressors 两类特异转录因子是激活蛋白和阻遏蛋白 A2-1→ 4.4.1 Activators / 激活蛋白 A2-2→ 4.4.2 Repressors / 阻遏蛋白 A3-1→ Enhancers / 增强子 A3-2→ Silencers / 沉默子 A4→ 4.5.1 DNA-Binding Motifs in Prokaryotes 原核生物DNA结合基序