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Unformatted text preview: 204-325 1 Summary of the Last Lecture Protein sequence is encoded by its gene. Gene products (enzymes) can work in specific order in a biochemical pathway. Single gene mutations account for many, but not all, genetic diseases in human. Genes also make proteins that are not enzymes. Mutations of these genes can also cause inheritable disorders. Genetic counseling involves genotype analysis, explaining consequence and presenting options 2 Today's Topics 1. Structure, Function and Synthesis of RNA 2. Transcription in Prokaryotes 3. Transcription in Eukaryotes 4. Post-Transcriptional Modifications: Capping, Tailing, Splicing, Editing, Processing and Base Modification 5. Difference between Prokaryotic and Eukaryotic Transcription
3 The Central Dogma Replication DNA
Transcription Gene Expression RNA
4 Topic 1 Structure, Function and Synthesis of RNA 5 Transcription Process 6 RNA Polymerase Catalyzes Transcription 7 Either of the DNA Strands can be the Template 8 Transcription of Two Genes 9 Animation 1: Transcription 10 Types of RNA Messenger RNA (mRNA) encodes the amino acid sequence of a polypeptide. Transfer RNA (tRNA) brings amino acids to ribosomes during translation. Ribosomal RNA (rRNA) combines with proteins to form a ribosome, the catalyst for translation. Small nuclear RNA (snRNA) combines with proteins to form complexes used in eukaryotic RNA processing. MicroRNA (miRNA) regulates mRNA translation and stability in eukaryotes.
11 mRNA 12 tRNA 13 rRNA 14 Topic 2 Transcription in Prokaryotes
15 Promoter, RNA-coding Sequence, and Terminator 16 Promoter Sequence for 70 Regulated Genes in E. coli 17 E. coli RNA Polymerase (RNAP) Protein Composition RNA Polymerase: No Primer Required X2 ' Core enzyme Holoenzyme binds promoter 70 :TTGACA(-35)...TATAAT(-10) (default) 32 :CCCCC(-39)...TATAAATA (-15) (heat shock) 54 :GTGGC(-26)...TTGCA(-14) (N starvation) 23 :TATAATA(-15) (T4 infection)
18 Transcription Initiation and Elongation 19 -Independent Termination in Some Genes 20 -Dependent Termination in Other Genes 21 rRNA Transcription and Processing in E. coli 22 Topic 3 Transcription in Eukaryotes
23 RNA Polymerases in Eukaryote RNA Polymerase I rRNA (28s, 18s, 5.8s) mRNA snRNA tRNA rRNA (5s) snRNA RNA Polymerase II RNA Polymerase III 24 Initiation of Transcription by RNA Polymerase I TBP + 3TAFs Upstream Binding Factor 25 Basal Transcription by RNA Polymerase II 26 RNA Polymerase II Promoter Structure (DNA Sequence) Promoter (up to -200) Proximal Element Core promoter (up to -50) GC Box (-90):GGGCGG Cat Box (-75): CAAT TATA Box (-30):TATAAAA Enhancer: Silencer: Initiator Usually several kb away, but could be more than 100kb away
27 Activation of RNA Polymerase II Transcription 28 Transcription Initiation by RNA Polymerase III 5s rRNA and tRNAs genes use Internal Control Region (ICR) as promoters RNA Pol III transcribed snRNA genes use upstream promoters (not shown) 29 Comparison of Genes Transcribed by RNAP I, II and III rRNA mRNA C tRNA 30 Topic 4 Post-Transcriptional Modifications: Capping, Tailing, Splicing, Editing, Processing and Base Modification
31 Capping, Tailing and Splicing for Eukaryotic mRNA 5' UTR 3' UTR 32 5 Capping of Eukaryotic mRNA 5' to 5' Linkage 33 Formation of mRNA 3 Poly (A) Tail in Eukaryote poly (A) consensus sequence 34 Splicing: Remove Intron 35 Steps of Splicing in Eukaryotic mRNA Y=C or U R=A or G N=A, C, G or U 2' to 5' linkage 36 snRNPs Form a Spliceosome for Splicing 37 Animation 2: mRNA Splicing 38 From Pre-mRNA to Mature mRNA in Eukaryotes 5'UTR 3'UTR 39 Group I Intron Self-splicing in rRNA (an Example of Ribozyme) 40 Intron removal in tRNA by Splicing Endonuclease and Ligase 41 RNA Editing Trypanosome Mitochondrial Cytochrome Oxidase III (COIII) Gene UU Edited 42 Guide RNA (gRNA) as Template for Editing 43 Tissue Specific Editing of Apolipoprotein mRNA 44 Processing of Pre-rRNA in Eukaryotes 45 Processing of pre-tRNA 46 Base Modifications in tRNA D GMe GMe 2 IMe 47 Topic 5 Difference between Prokaryotic and Eukaryotic Transcription
48 Comparison of Prokaryotic and Eukaryotic mRNA 49 Coupled Transcription and Translation in Prokaryotes 50 Functional Compartments in Eukaryotes 51 Comparison of mRNA Transcription in Prokaryotes and Eukaryotes 52 Animation 3: mRNA 53 Summary Genes are transcribed into RNA first in order to be expressed. Transcription is regulated by promoter sequence and catalyzed by a single RNA polymerase in prokaryotes. In eukaryotes, transcription is regulated by promoter, enhancer, as well as internal control region and upstream activator sequence; and is catalyzed by three RNA polymerases. RNA can be modified by capping, poly A tailing, splicing, editing and base modification after transcription.
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