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Transcription

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4. Terminator. 6. 1. DNA template. ???????? 1 strand ???????? Template strand ... 4. Terminator. ???? sequence ??? signal ???? transcription ... – PowerPoint PPT presentation

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Title: Transcription


1
Transcription
2
Transcription
  • ????????????????????????? (genetic information)
  • ??? DNA (double-stranded) ?????????????????
    RNA (single-stranded
  • ????????
  • ??????????????????? (copy) RNA ??? gene
  • ????????????????? RNA Synthesis

3
Link ??????? Transcription Translation
4
?????? Transcription
  • 1. Factors ??? transcription
  • 2. Direction ??? transcription
  • 3. Mechanism ??? transcription
  • 4. Control ??? transcription ?? Prokaryotic cells
  • 5. Control ??? transcription ?? Eukaryotic cells
  • 6. Mechanism ??? RNA splicing
  • 7. Reverse transcription

5
Factors ??????? Transcription
  • 1. DNA template
  • 2. RNA polymerase
  • 3. Promoter
  • 4. Terminator

6
1. DNA template
  • ???????? 1 strand ???????? Template strand
  • Strand ??????? ???????? Nontemplate strand
  • RNA ???????? nontemplate ?????? U ??? T
  • ???? mRNA ?????????? Sense strand ???? base
    ?????? nontemplate strand
  • ??????????? base ??? strand ?????????????????
    base ??? gene

7
Template and Nontemplate strands
8
???????????? DNA Template ?????? Transcription
  • Gene ????? DNA ???????? transcribed ?????? 3
    ????????????????????
  • promoter...structural gene.terminator

9
  • Promoter
  • ???? sequence ??????? DNA ????????? RNA
    polymerase ?????????????????????? RNA
  • promoter ???????? startpoint ( 1) ???
    structural gene ???????????????? nucleotide ???
    promoter ???? ?? (-)
  • Terminator sequence
  • ???? sequence ??????? DNA ?????????????? gene
    ?????????? Transcription

10
2. RNA polymerase
  • ?????????????????????????????????
    ?????????????????????? Holoenzyme
  • ?????????? 2 components ???? ???
  • Sigma (s) factor ?????? ???????? transcription
    ????????????????
  • Core polymerase ??????????????? DNA template
    ?????? RNA nucleotides ??????????????????
    transcription

11
  • RNA polymerase ?? 5 subunits ???
  • - 1 s (Sigma) subunit
  • - 2 a (Alpha) subunits
  • - 2 b (Beta) subunits

12
  • RNA polymerase ?????????????????? proofreading
  • ?????????????? nucleotides ???????????????????
    ??
  • ?????? proofreading ???????? ????? RNA
    ??????????
  • ??? ??????????? copies ???????????????????

13
3. Promoter
  • ???? regulatory sequence ?? DNA ??????? binding
    site ??? RNA polymerase ????? start transcription
  • ???? signal ?????? initiation ??????????? DNA
    strand ??????? transcribed
  • Transcription ????????????????????????????????????
    ?????????? promoter ??????????? RNA polymerase
    ??????????????

14
Promoter ??????????????? RNA Polymerase Closed
promoter ???? weak promoterOpened promoter ????
strong promoter
15
4. Terminator
  • ???? sequence ??? signal ???? transcription
  • Terminator site ???? inverted repeat sequence ??
    DNA template ??? ?? RNA ???????????
  • ?? DNA form ????????????? (Cruciform structure)
  • ?? RNA form ???? Stem-loop structure ???? base
    ??????????????? transcribed

16
Terminator sequences?? DNA ????? RNA
17
  • Terminator ????????????? protein
    ???????????????????? transcription ???? rho (r)
    ???? NusA protein
  • RNA polymerase ?? terminator site ???
  • ????? RNA polymerase ??????? DNA template
  • ???? transcription ???????????????????
    protein ?????
  • RNA polymerase ?? termination site ??????????
    protein ????? ????????? transcription

18
Direction ??? Transcription
  • RNA ???????????????????
  • ??? 5 ---gt 3
  • ??? nucleotides ??????????????????????????????
    3 ??? nucleotides ?????????????

19
  • ???????????????????? RNA polymerase
  • ?????? ?????????? DNA ?????? Promoter
    ??????????? start point
  • DNA template ????????????????
  • (unwind) ?????????????
  • ????????????????????? (rewind)
  • ?????? RNA polymerase ?????????

20
  • Mechanism ??? Transcription
  • 1. Initiation
  • 2. Elongation
  • 3. Termination

21
1. Initiation of Transcription
  • ??????? Promoter ??? RNA polymerase
  • 1.1 Promoter
  • ???? sequences ???? start point ????????????
    upstream ?? (-) 1 ???????????????????
  • Start point ?? structural gene ????????????
    downstream ??? () 1 ?????????????????????????????
    ???

22
  • 1.2 RNA polymerase
  • Holoenzyme ??????????????? promoter ????????
  • Closed promoter
  • s factor ??????????? promoter ????????? core
    enzyme
  • ????? promoter ???????????????????
  • Core enzyme ??? DNA ??????? Opened promoter
    ????????????????????? s factor ??????? start
    point
  • Core enzyme ??? RNA nucleotide ????????? start
    point
  • ????????????????? s factor ???????????? promoter

23
Initiation of transcription
24
2. Elongation of Transcription
  • Core ??? RNA polymerase ???????????? RNA
    nucleotides ??????? 3 - OH ????????????
    nucleotide ????????????? ??? ????????????????
    ?????? RNA ????????? 5 ---gt 3
  • RNA ??? synthesis ??????????? complementary
    ??????? DNA template
  • ???? RNA ??????? synthesis ???????????????????????
    template ??? template ???????????????? DNA
    duplex

25
Elongation of transcription?????????? core
enzyme ??? holoenzyme RNA polymerase
?????????????????????? RNA ?????
26
Termination of Transcription
  • RNA polymerase ?????????? terminator ??????
    transcription
  • Terminator ?? 2 types ???
  • 1) Rho - dependent terminator
  • 2) Rho - independent terminator
  • Terminator ???? 2 types ???????????? ??
  • inverted repeat sequence ?? DNA ??? RNA

27
  • 1) Rho-dependent terminator
  • Rho r ?????? RNA ???
  • ?????????? ???? RNA ?????
  • ??? RNA polymerase ???
  • terminator
  • ????? RNA polymerase ????
  • ???? terminator ??????
  • ???? transcription
  • ???????? ? ????????????

28
  • 2) Rho-independent terminator
  • ???? transcription
  • ???????? rho protein
  • ??? Terminator
  • ??????? DNA ??
  • base A ???
  • ??? ?? RNA ??
  • base U ???
  • ???? stem-loop ????????????????? A-U base
    pairs ???
  • ??????? ??? stable ???? ????????? RNA ???
  • RNA polymerase ?????????? DNA
    ???????transcription

29
RNA Script
30
RNA Script
  • RNA ??? transcribed ?????????????? gene ????
    ????? RNA polymerase ???????????? gene ???????
    ?????? promoter
  • RNA script ????????????? (processing)
    ????????????????
  • 1. 5 leader segment ????????????? start point
  • 2. Protein-coding sequence ??? gene
  • 3. 3 trailer segment ??????? terminator

31
(No Transcript)
32
Transcriptional Control in Prokaryote
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