Eukaryotic Transcription 真核生物的转录
Eukaryotic Transcription 真核生物的转录
Key Concepts Differences between Prokaryotes and Eukaryotes Three kinds of rna polymerases(, Il, and IID) in eukaryotic cells Promoters and enhancers Upstream regulatory elements Transcription factors
Key Concepts • Differences between Prokaryotes and Eukaryotes • Three kinds of RNA polymerases (I, II, and III) in eukaryotic cells • Promoters and Enhancers • Upstream regulatory elements • Transcription factors
Similarities to that in prokaryotic cells Don t require a primer Synthesize rna in a 5 to 3 direction RNa complementary to the antisense template strand
Similarities to that in prokaryotic cells • Don’t require a primer • Synthesize RNA in a 5’ to 3’ direction • RNA complementary to the antisense template strand
Differences between Prokaryotes and Eukaryotes There are 3 RNa polymerases Require more accessory factors for binding promoter dna initiating transcription The C-terminus of rna Pol Ii largest subunit contains a stretch of heptapeptide repeats, named as carboxyl terminal domain (CTD) Amino acid sequence: Tyr-Ser-Pro-Thr-Ser-Pro-Ser. Repeated 26X (yeast)& 52x in mouse Involved in polymerase phosphorylation during elongation The CTd is unphosphorylated at transcription initiation, and phosphorylation occurs during transcription elongation as the RNa Pol II leaves the promoter (In vitro results) Because it transcribes all eukaryotic protein-coding gene, RNA Pol II is the most important rna polymerase for the study of differential gene expression. The Ctd is an important target for differential activation of transcription elongation
Differences between Prokaryotes and Eukaryotes • There are 3 RNA polymerases • Require more accessory factors for binding promoter DNA & initiating transcription • The C-terminus of RNA Pol II largest subunit contains a stretch of heptapeptide repeats, named as carboxyl terminal domain (CTD) • Amino acid sequence: Tyr-Ser-Pro-Thr-Ser-Pro-Ser. Repeated 26 x (yeast) & 52x in mouse • Involved in polymerase phosphorylation during elongation • The CTD is unphosphorylated at transcription initiation, and phosphorylation occurs during transcription elongation as the RNA Pol II leaves the promoter(In vitro results) • Because it transcribes all eukaryotic protein-coding gene, RNA Pol II is the most important RNA polymerase for the study of differential gene expression. The CTD is an important target for differential activation of transcription elongation
Key Terms a basal factor is a transcription factor required by RNa polymerase Il to form the initiation complex at all promoters. Factors are identified as TFIX whereⅩ is a number The basal transcription apparatus is the complex of transcription factors that assembles at the promoter before Rna polymerase is bound An enhancer is a cis-acting sequence that increases the utilization of(some)eukaryotic promoters, and can function in either orientation and in any location (upstream or downstream) relative to the promoter
Key Terms • A basal factor is a transcription factor required by RNA polymerase II to form the initiation complex at all promoters. Factors are identified as TFIIX, where X is a number. • The basal transcription apparatus is the complex of transcription factors that assembles at the promoter before RNA polymerase is bound • An enhancer is a cis-acting sequence that increases the utilization of (some) eukaryotic promoters, and can function in either orientation and in any location (upstream or downstream) relative to the promoter
Key Concepts rna polymerase i synthesizes rrNa in the nucleolus RNa polymerase ii synthesizes mrNa in the nucleoplasm RNa polymerase III synthesizes small RNAS in the nucleoplasm The largest subunit in rna polymerase ll has a Ctd(carboxy-terminal domain) consisting of multiple repeats of a septamer
Key Concepts • RNA polymerase I synthesizes rRNA in the nucleolus • RNA polymerase II synthesizes mRNA in the nucleoplasm • RNA polymerase III synthesizes small RNAs in the nucleoplasm • The largest subunit in RNA polymerase II has a CTD (carboxy-terminal domain) consisting of multiple repeats of a septamer
Eukaryotic RNa polymerases RNA Po|位置 产物 相对活性α-鹅膏蕈的敏感 Po!|核仁28s,18s,5.8 s rrnas 50~70% 不敏感 Po‖核质 hnRNA,mRNA,某些 SnRNA20~40% 高度敏感 PolⅢ核质tRNA,5 SrrnA,某些 SnRNAs~10%片段特异,中等敏感 Other RNa polymerases in Eukaryotic cell Chloroplast rna polymerases叶绿体 mitochondria RNa polymerases线粒体
Eukaryotic RNA polymerases RNA Pol位置 产物 相对活性 α-鹅膏蕈的敏感 Pol Ⅰ 核仁 28s,18s,5.8s rRNAs 50～70% 不敏感 Pol Ⅱ 核质 hnRNA,mRNA,某些SnRNA 20～40% 高度敏感 Pol Ⅲ 核质 tRNA,5SrRNA,某些SnRNAs ～10% 片段特异，中等敏感 Other RNA polymerases in Eukaryotic cell Chloroplast RNA polymerases 叶绿体 mitochondria RNA polymerases 线粒体
真核RNA聚合酶的活性 ·转录时,按5′3′方向合成RNA链; 底物为4种三磷酸核苷酸:ATP,GTP,UTP和 CTP 不需要引物; 需要其它起始蛋白的存在,聚合酶才能与启 动子结合并诱导起始;
真核RNA聚合酶的活性 •转录时，按 5’ 3’方向合成RNA链； •底物为4种三磷酸核苷酸：ATP,GTP,UTP 和 CTP； •不需要引物； •需要其它起始蛋白的存在，聚合酶才能与启 动子结合并诱导起始；
RNA聚合酶的组成 ·3种聚合酶都由2个大亚基,12个以上的小亚基 组成 ·在3种聚合酶之间,最大2个亚基,至少5个小 亚基的基因编码区具有同源性;4-7种小亚基 为各种RNA聚合酶特有; ·都具有原核RNA聚合酶核心α2BB′同源的亚基 最大亚基与β′相似,次最大亚基邬β相似
RNA 聚合酶的组成 • 3种聚合酶都由2个大亚基，12个以上的小亚基 组成； • 在3种聚合酶之间，最大2个亚基，至少5个小 亚基的基因编码区具有同源性；4-7种小亚基 为各种RNA聚合酶特有； • 都具有原核RNA聚合酶核心2’同源的亚基; • 最大亚基与’相似，次最大亚基与相似；
Eukaryotic rna polymerases consist of many subunits The general Size No Features constitution of a KD Related to bactenal subunit R 200 eukaryotic rna binds dna has CTD =(YSPTSPS polymerase least n=26: mouse n=52 Related to bacterial subunit B enzyme 100 binds nucleotides astypitied in cerevisiae 50 2 Related to bacterial subunit o 2 Common to all 3 polymerases 25 Common to all 3 polymerases Common to all 3 polymerases
Eukaryotic RNA polymerases consist of many subunits • The general constitution of a eukaryotic RNA polymerase II enzyme astypified in S. cerevisiae