生物化学教案 第十三章RNA的生物合成.doc

课程名称_生物化学_授课题目第十三章RNA的生物合成Chapter 13 RNA Biosynthesis授课日期授课班级授课时数4授课方式多媒体授课内容与时间分配第一节参与RNA合成的的酶类与因子（ 1.0学时 ） (Enzymes and factors involved in RNA biosynthesis)一、转录与复制的异同 (Similarities and differences between transcription and replication)二、RNA聚合酶（DNA依赖的RNA聚合酶）(RNA polymerase; DNA dependent RNA polymerase) 作用条件：1. 4种NTP2. Mg2+或Mn2+3. DNA模板4. 53方向，不需要引物（一）原核生物的RNA聚合酶 1. 核心酶2和全酶2亚基组成2. 各个亚基的功能 （二）真核生物的RNA聚合酶 三种类型RNA聚合酶I、 II 、III、各自所在部位、转录产物、以及对鹅膏蕈碱敏感度。第二节 真核生物转录过程 （1.5 学时） (RNA transcription in eukaryotes)起始、延长、终止三步一、起始 (Initiation) 1.几个概念 反义链/-链/模板链 (antisense/-/template strand)：The strand that serves as template for RNA synthesis is called the template strandor antisense strand. 有意义链/+/密码链 (sense/+/coding strand)：The opposite DNA strand, which has the same base sequence as the RNA transcript (U replacing T) is called non-template strand, or coding strandor sense strand.2.启动子（Promoter）的定义与结构 -10 sequence(Pribnow box): TATAAT-35 sequence: TTGACA3.起始的发生 首先，闭合的启动子复合物( closed promoter complex ) 和开放的启动子复合体(open promoter complex) 的形成。然后，RNA的合成。 授课内容、教具与时间分配合成的特点：(1)5端第一个核苷酸往往是pppG或pppA(2)不需引物(3)合成方向，53方向。4.待转录基因的选择与转录的进行方向 二、延长 (Elongation) 三、终止 (Termination) 第三节 真核生物的转录后加工 （0.5学时）(Processing of Eukaryotic RNA)一、 mRNA的转录后加工 (Processing of Eukaryotic mRNA) 1. 加帽：5端加mGpppG三磷酸双鸟苷2. 加尾：3端poly A 尾巴3. mRNA前体的剪接4. RNA编辑二、tRNA的转录后加工 (Processing of Eukaryotic tRNA) 三、rRNA的转录后加工 (Processing of Eukaryotic rRNA) 第四节 原核生物的转录（1.0学时）(RNA transcription in prokaryotes)一、起始 (Initiation)二、过程 (Process)：亚基脱落，核心酶构象发生变化，并沿模板链35方向快速滑动，同时转录产物沿5 3方向延长。概念：转录泡 (transcription bubble) 结构的组成。The two strands of the double-helical DNA molecule are separated by the enzyme to form a “transcription bubble”.三、终止 (Termination) 因子：一种蛋白质，由六个亚基组成的六聚体，具有ATP酶活性能与单链RNA结合，但不能与DNA双链或RNADNA杂和双链结合。依赖因子的终止：不依赖因子的终止：在DNA模板含有终止信号（回文结构），因此转录出来的RNA能自身互补形成发夹结构，在发夹的3尾端有4个或更多的U。RNA聚合酶遇到这种发夹结构即停止工作。由于含有连续多个微弱的U-A碱基对，因而新生的RNA即自模板分理出。四、转录的抑制剂 (Inhibitors of transcription) （一）与DNA模板作用的转录抑制剂 放线菌素D（二）与RNA聚合酶作用的转录抑制剂 利福平 / 利福霉素 鹅膏蕈碱五、RNA复制 (RNA replication)要求学生掌握的英语内容RNA synthesis or transcription is the process of transcribing the information of DNA nucleotide sequence into RNA sequence. All cellular RNA molecules are synthesized by RNA polymerases. The basic reaction of RNA synthesis is the formation of a phosphodiester bond with the concomitant release of a pyrophosphate. There are three distinct DNA-dependent RNA polymerases in the nuclei of eukaryotic cells. RNA polymerase I, II, and III direct the transcription of rRNA, mRNA and tRNA, respectively. RNA synthesis occurs in three stages: initiation, elongation, and termination. Transcription initiation requires specialized DNA sequences called promoters. The recognition of promoter sequences involves transcription factions and RNA polymerases. The precursors of mRNA in eukaryotic cells undergo the most extensive processing including 5-end capping and a poly(A) tail adding at the 3-end. Introns are removed by splicing reactions. During the splicing reactions, the exons are connected and the mature mRNA is produced. Other post-transcriptional modifications of mRNA include the alternative splicing and RNA editing. The eukaryotic 18S, 5.8S and 28S rRNAs are transcribed as a 45s precursors which are excised and modified to form the mature rRNAs. Eukaryotic tRNA transcripts also require the excision of a short intron and enzymatic addition of a 3-terminal CCA to form the mature tRNA. The basic biochemistry of RNA synthesis in prokaryotes is similar to that in eukaryotes except that RNA synthesis in the latter is much more complex. In prokaryotes such as E. coli, a single kind of RNA polymerase is responsible for the synthesis of three different types of RNA (rRNA, mRNA, tRNA). Its mRNA processing is limited. Transcription and translation in prokaryotes are closely coupled and take place in the same compartment. The primary