Chapter 10 Eukaryotic RNA Polymerases and Their Promoters Copyright The McGraw-Hill Companies,Inc.Permission required for reproduction or display. David A.Bushnell,Kenneth D.Westover,and Roger D.Komberg
Chapter 10 Eukaryotic RNA Polymerases and Their Promoters
Prokaryotes have only one RNA polymerase that makes three kinds of RNAs (mRNA,rRNA,and tRNA)(switch o-factor,the core enzyme is same) What is the situation in eukaryotes? 10-2
10-2 Prokaryotes have only one RNA polymerase that makes three kinds of RNAs (mRNA, rRNA, and tRNA)（ switch σ-factor，the core enzyme is same) What is the situation in eukaryotes?
10.1 Multiple Forms of Eukaryotic RNA Polymerase Ribosomal genes are different from other nuclear genes GC content(60%),compared with the rest of the DNA(40%) Unusually repetitive Nucleolus (is the site to synthesize rRNAs There are at least two RNA polymerases operating in eukaryotic nuclei One transcribes major ribosomal RNA genes One or more to transcribe rest of nuclear genes 10-3
10-3 10.1 Multiple Forms of Eukaryotic RNA Polymerase ✓ Ribosomal genes are different from other nuclear genes – GC content (60%), compared with the rest of the DNA (40%) – Unusually repetitive – Nucleolus (核仁) is the site to synthesize rRNAs ✓ There are at least two RNA polymerases operating in eukaryotic nuclei – One transcribes major ribosomal RNA genes – One or more to transcribe rest of nuclear genes
Three Nuclear Polymerases Eukaryotic nuclei contain three RNA polymerases -These can be separated by ion-exchange chromatography RNA polymerase I found in nucleolus -Location suggests in transcribes rRNA genes RNA polymerases ll and Ill are found in the nucleoplasm(核浆) 10-4
10-4 Three Nuclear Polymerases ✓ Eukaryotic nuclei contain three RNA polymerases – These can be separated by ion-exchange chromatography ✓ RNA polymerase I found in nucleolus – Location suggests in transcribes rRNA genes ✓ RNA polymerases II and III are found in the nucleoplasm (核浆)
Roles of the Three RNA Polymerases √Polymerase I makes Table 10.1 Roles of Eukaryotic RNA Polymerases large rRNA precursor RNA Cellular RNAs Mature RNA √Polymerase ll makes Polymerase Synthesized (Vertebrate) Large rRNA precursor 28S,18S,and -Heterogeneous 5.8S rRNAs hnRNAs mRNAs nuclear RNA(核不均一 snRNAs snRNAs 5S rRNA precursor 5S rRNA RNA,hnRNA) tRNA precursors tRNAs U6 snRNA(precursor?) U6 snRNA -Small nuclear RNA 7SL RNA (precursor?) 7SL RNA 7SK RNA (precursor?) 7SK RNA √Polymerase Ill makes precursors to tRNAs, 5S rRNA and other small RNA 10-5
10-5 Roles of the Three RNA Polymerases ✓ Polymerase I makes large rRNA precursor ✓ Polymerase II makes – Heterogeneous nuclear RNA (核不均一 RNA, hnRNA) – Small nuclear RNA ✓ Polymerase III makes precursors to tRNAs, 5S rRNA and other small RNA