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Transcription of Eukaryote

Transcription of Eukaryote. Promoters: - TATA box - CAAT box (CCAAT box) - GC box - ~ 200 bp upstrean of startpoint (mostly) - work with RNA pol. / transcription factors. Enhancers: - stimulate initiation - ~ 100 bp - upstream / downstream

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Transcription of Eukaryote

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  1. Transcription of Eukaryote Promoters: - TATA box - CAAT box (CCAAT box) - GC box - ~ 200 bp upstrean of startpoint (mostly) - work with RNA pol. / transcription factors Enhancers: - stimulate initiation - ~ 100 bp - upstream / downstream - interact with transcriptional factors

  2. PROMOTERS: - TATA box (center at -30) - CAAT box (seq. at -75) - GC box ( seq. at -90); GGGCGG

  3. Eukaryotic RNA polymerases RNA pol. I rRNA RNA pol. II mRNA RNA pol. III tRNA & other small RNA

  4. RNA Pol. I has a bipartite Promoters Increase efficiency by the upstream control elements (UCE)

  5. RNA pol. III uses both downstream and up stream ppromoters

  6. TF IIIB ; Initiation factor / Positioning factor TF IIIA & TF IIIC ; Assembly factors

  7. TBP = TATA box binding protein TAFs = TBP-associated factors RNA Pol II require ATP hydrolysis (TF IIE) & helicase activity (TF IIH) for Pol. movement

  8. A model of phosphorylation to release RNA Pol II from TF for elongation

  9. Fig.22.2 Overview: Addition to the 5’ and 3’ ends, Splicing to remove introns

  10. SPLICING REACTION: by transesterification reaction; breaking and making of bonds Two stages of splicing: First st.; cut at 5’ splice site, right intron-exon mol. form a lariat 2 nd st.; cut at 3’ splice site, release free intron, right exon ligated to the left exon

  11. Cis-splicing trans-splicing reaction

  12. tRNA splicing is different mechanism: separate and ligate tRNA splicing depends on a secondary structure rather than sequence of the intron 1st step: phosphodiester bond cleavage by endonuclease 2nd step: require ATP, bond formation by RNA ligase

  13. Group I intron: Self-splicing by transesterification Reaction require: - a monovalent cation, a divalent cation, - a guanine nucleotide cofactor (only G), must have a 3’-OH group

  14. FIG.23.2 Self-splicing OR Autosplicing of Group I introns

  15. Some introns code for Proteins: - Endonuclease - Reverse transcriptase - Muturase: for splicing Fig. 23.11Endonuclease: - make a double-strand break in DNA - duplicated-intron inserted at the break

  16. Fig.23.12 Endonuclease / Reverse transcriptase

  17. 5’ END of eukaryotic mRNA is capped Transcription: - start with nucleoside triphosphate (purine A or G) - first nucleotide retains 5’ triphosphate group - addition of the 5’ terminal G catalyzed by a nuclear enz., guanylyl transferase - the new G, in reverse orientation, called CAP

  18. 3’ ENDS OF EUKARYOTIC mRNA - RNA Pol I & Pol III terminate like bact. RNA Pol - RNA Pol I; recognize of an 18 base termination seq. - RNA Pol III; recognize at the second U within a run of 4U bases - RNA Pol II; loosely specified by cleavage / polyadenylation - seq. AAUAAA locate from 11 to 30 nts upstream of poly A site / provide the signal for both cleavage / polyadenylation

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