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Lecture 13

Lecture 13. Chapter 5 mRNA Modifica- tions in Eukaryotes 5.1 Capping 5.2 Polyadenylation 5.3 Splic ing 5.4 mRNA Editing 5.5 Experiments. 第 5 章 真核生物 mRNA 的修饰 5.1 加帽 5.2 聚腺苷酸化 5.3 剪 接 5.4 mRNA 编辑 5.5 实验研究. Revision: chapters 1 to 5.

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Lecture 13

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  1. Lecture 13 Chapter 5 mRNA Modifica- tions in Eukaryotes5.1 Capping 5.2 Polyadenylation 5.3Splicing 5.4 mRNA Editing 5.5 Experiments 第5章 真核生物 mRNA的修饰 5.1 加帽 5.2 聚腺苷酸化 5.3剪接 5.4 mRNA编辑 5.5 实验研究 Revision: chapters 1 to 5.

  2. Any findings about rRNA and tRNA?关于rRNA和tRNA有什么发现吗? Q1 → Do rRNA and tRNA have 5’ cap, 3’ poly(A) tail and intron structures? Q2 → If they have, how are they added or removed? Q1 → rRNA和tRNA有没有5’帽、3’ poly (A)尾和内含子结构呢？ Q2 →如果有的话，它们是怎么加上去或去除的呢？

  3. Review of Lecture 12 A1→ Capping process / 加帽过程 A2→ Functions of the cap structure帽结构的功能 A3→ The polyadenylation mechanism 聚腺苷酸化机理 A4→ Functions of the poly(A) tailpoly(A)尾的功能 A5→ Splicing / 剪接 A6→ The splicing reaction / 剪接反应

  4. A1→ Capping process / 加帽过程

  5. A2→ Functions of the cap structure帽结构的功能 1. Helps prevent degradation帮助防止降解 2. Helps transport into cytoplasm帮助转运到细胞质中 3. Enhances translation / 增强转译 4. Helps remove the first intron帮助去除第一个内含子

  6. A3→ The polyadenylation mechanism 聚腺苷酸化机理 Poly(A)-Binding Protein

  7. A4-1→ Functions of the poly(A) tailpoly(A)尾的功能 The main function of poly(A) tail is to protect the mRNA from degradation by ribonucleases. AAAAAAA - - - - - - AAAA A AAAAAAA - - - A A A A A

  8. A4-2→ Functions of the poly(A) tailpoly(A)尾的功能 There is also some evidence that the poly-A tail is involved insplicing and enhances translation of mRNAs. AAAAAAA - - - - - - AAAA

  9. A5→ 5.3 Splicing / 剪接 Splicing: The process of removing introns from a pre-mRNA. 剪接：将内含子从前体mRNA去除的过程。

  10. A6→ The splicing reaction / 剪接反应

  11. Other mRNA modifications in eukaryotes 真核生物中的其它mRNA修饰 Self-splicing 自我剪接 Trans-splicing 反式剪接 Alternative splicing 可变剪接 mRNA editing mRNA编辑

  12. Questions for Lecture 13 Q1→ Can an intron remove itself?内含子能把自己去除吗? Q2→ What is trans-splicing? How does it occur? 什么是反式剪接？它是如何进行的？ Q3→ Will an intron always be removed? 内含子是否一定要被去掉? Q4→ What is RNA editing?RNA编辑是怎么回事？

  13. Vocabulary of Lecture 13 (1/2) tetrahymena self-splicing group I intron group II intron introns-early theory introns-late theory alternative splicing immune cell antibody antigen 四膜虫 自我剪接 I类内含子 II类内含子 内含子早现说 内含子晚现说 可变剪接 免疫细胞 抗体 抗原

  14. Vocabulary of Lecture 13 (2/2) secret secrete RNA editing guide RNA, gRNA protozoa trypanosome African sleeping sickness apolipoprotein inosine 秘密（的） 分泌 RNA编辑 指导RNA 原生生物 锥虫 非洲昏睡病 载脂蛋白 次黄苷

  15. Q1→ Can an intron remove itself?内含子能把自己去除吗?

  16. A1→ 5.3.3 Self-Splicing / 自我剪接 自我剪接：一些mRNA不需要外来因子如snRNPs的帮助而将其中的内含子剪接掉的过程。 Self-splicing:The process of some mRNAs to splice out introns without help from outside factors like snRNPs. Tetrahymena thermophilia 嗜热四膜虫

  17. Self-splicing of group I intronI类内含子的自我剪接 Group I introns:Self-splicing introns that use a free guanylate nucleotide in the splicing mechanism. I类内含子：自我剪接型内含子，在剪接过程中使用鸟苷酸。

  18. Self-splicing of group II intronII 类内含子的自我剪接 Group II introns:Self-splicing introns that follow nearly the same basic splicing reaction as normally occurs with the spliceosome. II类内含子：自我剪接型内含子，剪接过程几乎与有剪接体参与的剪接反应相同。 Without help of proteins

  19. Normal splicing and Self-splicing普通剪接与自我剪接 Normal splicing Self-splicing With help of proteins Without help of proteins

  20. Q2→ What is trans-splicing? How does it occur? 什么是反式剪接？它是如何进行的？ The scenery is much better here … 风景这边独好……

  21. A2→ 5.3.4 Trans-Splicing / 反式剪接 反式剪接：将来自不同转录单位的两段RNA拼接在一起的过程。 Trans-splicing:The process of splicing together two RNA fragments transcribed from separate transcription units. DNA Mature mRNA Protein RNA piece of separate origin

  22. Trans-Splicing / 反式剪接 来自前体mRNA中腺嘌呤核苷酸上的羟基能够进攻SL-RNA的5’剪接位点、去除内含子部分并帮助SL连接到前体mRNA上。这一过程称为反式剪接，因为被连接到一起的RNA片段来自于不同的基因。

  23. Trans-splicingvs. Normal splicing 反式剪接vs. 普通剪接 What is different between them?

  24. 5.3.5 Reasons for Introns内含子存在的原因 Introns-early theory Intron: “Why am I here?” Introns-late theory

  25. Intron-early theory / 内含子早现说 E. coli “Could be. Who knows?!” “I heard somebody say E. coli once had introns. Is that true?”

  26. Intron-late theory / 内含子后现说 E. coli “We are the ones having introns! We are proud of it.”

  27. Q3→ Will an intron always be removed? 内含子是否一定要被去掉? “I don’t wonna come out. Please allow me to stay.”

  28. A3→ Alternative splicing / 可变剪接 可变剪接：通过选择包含或不包含某些内含子和外显子而从一个编码区产生不同蛋白质的过程。 Alternative splicing:The process of making various proteins from one coding region by choosing between the inclusion/exclusion of certain introns and exons.

  29. One pre-mRNA, multiple mature mRNAs 一种前体mRNA，多种成熟mRNA

  30. Alternative splicing in immune cells免疫细胞中的可变剪接 通过对其基因转录产物采用可变剪接，免疫细胞可以决定抗体是要被固定在细胞膜上还是要被分泌到细胞外。

  31. Drosophila Dscam gene Exon 4 Exon 6 Exon 9 Exon 3 Exon 5 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 4.10 4.11 4.12 Alternative Splicing Goes Mainstream 可变剪接成为主流 The Scientist, Volume 17(24): 28, Dec. 15, 2003

  32. Q4→ What is RNA editing?RNA编辑是怎么回事？ Audio editing 音频编辑 Picture editing 图片编辑 RNA editing ?

  33. A4→ 5.4 mRNA Editing / mRNA编辑 mRNA编辑：通过向前体mRNA中加入或从中去除特殊核苷酸来产生成熟mRNA的过程。 mRNA editing:The process of making a mature mRNA molecule by addition or removal of specific nucleotides in pre-mRNA. COⅡ DNA: - - - GTATAAAAGTAGA G A ACCTGG - - - COⅡ RNA: - - - GTATAAAAGTAGATTGTATACCTGG - - -

  34. The sleeping sickness / 嗜睡病 Sleeping sickness is one of the most neglected human diseases, and mainly affects the most deprived peoples of some African countries. Why the patient is so sleepy? Trypanosome锥虫

  35. RNA editing in trypanosome 锥虫线粒体基因产生的是未完成的mRNA转录产物，还需要向其中添加或去除尿苷酸（U）。 一种称为指导RNA（gRNA）的特殊RNA分子与转录产物杂交。

  36. CU editing/ CU 编辑

  37. In the liver …/ 在肝脏中…

  38. In small intenstine … / 在小肠中 …… ing

  39. A  I editingin GluR-B mRNA Glutamate receptor subunit GluR-B mRNA synapse Q Glu Glu Ga2+ - UUU AUG CAG CAA GGA - A  I editing Q R - UUU AUG CIG CAA GGA - >99.9% R in brain R www.lehigh.edu/~swm3/research.html

  40. A  I editingin GluR-B mRNA With normal editing With reduced editing www.nature.com/.../n1/fig_tab/nn0199_57_F4.html

  41. Essentials of Lecture 13 / 第13讲要点 A1→ Self-Splicing / 自我剪接 A2→ Trans-Splicing / 反式剪接 A3→ Alternative splicing / 可变剪接 A4→ mRNA Editing / mRNA编辑

  42. A1→ 5.3.3 Self-Splicing / 自我剪接 自我剪接：一些mRNA不需要外来因子如snRNPs的帮助而将其中的内含子剪接掉的过程。 Self-splicing:The process of some mRNAs to splice out introns without help from outside factors like snRNPs. Tetrahymena thermophilia 嗜热四膜虫

  43. A2→ 5.3.4 Trans-Splicing / 反式剪接 反式剪接：将来自不同转录单位的两段RNA拼接在一起的过程。 Trans-splicing:The process of splicing together two RNA fragments transcribed from separate transcription units. DNA Mature mRNA Protein RNA piece of separate origin

  44. A3→ Alternative splicing / 可变剪接 可变剪接：通过选择包含或不包含某些内含子和外显子而从一个编码区产生不同蛋白质的过程。 Alternative splicing:The process of making various proteins from one coding region by choosing between the inclusion/exclusion of certain introns and exons.

  45. A4→ 5.4 mRNA Editing / mRNA编辑 mRNA编辑：通过向前体mRNA中加入或从中去除特殊核苷酸来产生成熟mRNA的过程。 mRNA editing:The process of making a mature mRNA molecule by addition or removal of specific nucleotides in pre-mRNA. COⅡ DNA: - - - GTATAAAAGTAGA G A ACCTGG - - - COⅡ RNA: - - - GTATAAAAGTAGATTGTATACCTGG - - -

  46. Lecture 15 第6章 转译 6.1 遗传密码 6.2 原核生物转译机理 6.3 真核生物转译 6.4 tRNA结构与摇摆 6.5 实验研究 Chapter 6 Translation 6.1 The Genetic Code 6.2 Mechanism of Translation in Prokaryotes 6.3 Translation in Eukaryotes 6.4 tRNA Structure and Wobble 6.5 Experiments

  47. Questions for Lecture 15 Q1→ What is genetic code?什么是遗传密码？ Q2→ How is translation initiated in prokaryotes? 原核生物中翻译是如何启动的？ Q3→ What steps does the elongation process have? 延伸过程有哪些步骤？ Q4→ How is translation terminated?翻译是如何终止的？

  48. Review of Chapters 1 to 5 2010-10-22 (Day 14): Mid-term test • Mid-term test • 判 断 题（10个，每个2分，共20分）； • 单 选 题（10题，每题2分，共20分）； • 名 词 解 释（ 5个，每个3分，共15分）； • 问 答 题（ 5题，每题9分，共45分）。 • （第III、IV大题中各2题要求必须用英文答题）

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