????(gene expression)

1
?6? ???????
2
(No Transcript)
3
(No Transcript)
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????(gene expression)

• ????????????????????,?????,??????????????????

5
RNA ???

• 4?NTP?DNA???RNA???
• ????????????????
• ???????, ?5---3??
• ???????RNA???
• ????????????????
• ??????????????RNA

6
??????

• ????????mRNA?tRNA???????????????ATP?GTP?Mg
• mRNA????????????????
• tRNA??????,????????????
• ???????????????
• ??????????????????????

7
???????????

• ????(housekeeping gene)???????????????????????
• ???????(constitutive gene expression)?????????,???
  ????,??????????????????????????

8

• ????(induction expression)??????????????,?????????
  ?,???????????
• ????(repression expression)??????????,???????????

9

• ?????(temporal specificity)??????,????????????????
  ???,??????????????????????
• ?????(spatial specificity)????????,???????????????
  ??

10

• ????(coordinated expression)?????????,????,???????
  ????(coordinated regulation)

11
???????(gene expression regulation )

• ??????????????,???????????????????????????????????
  ????,??????????????

12
???????????

• ????????????
• ?????????

13
???????????

• ?????????
• ????????????
• ??DNA??
• ????
• DNA-???????-???????
• RNA???

14
Transcription
5 GATCTGACTGACATAGACATAGAT 3 coding (
non-template) strand 3 CTAGACTGACTGTATCTGTATCTA
5 template strand   5 GAUCUGACUGACAUAGACAUAGAU
3 mRNA
15
??????????????
16
? ???????(?)???????

• ???
• s??
• ????
• ?????
• ????
• RNA??????
• ???

17
???(operon)
???
???
???
????
18
? ? ?

• ?????????? E. coli??????40-60bp,??????????
• ????(initiation site) 1
• ????(binding site) -10bp,RNA???????
  T80A95T45A60A50T96
• ????(recognition site) -35bp,s??????
  T82G78A65C54A95

19
s??

• ?????s????????RNA???,????????????s??,????????????
• ????(repressor)
• ?DNA?????????,?????????????????

20
?????

• ?DNA???????,?????????????????
• CAP??(catabolic gene activator protein,CAP)
  ???????????
• ntrC?? ??????????????,????????ntrB?????(???)?????
  (???)????

21
E. coli Promoters
consensus
TATA (Pribnow) box
22
????(inversion protein)

• ???????????????H1?H2?????????????,????????????????
  ????
• ???(attenuator)
• ?????,???????????????,??????????????

23
RNA??????

• ????????????,RNA???????,RNA(rRNA,tRNA)???????
• ??????????(stringent response)

24
Positive vs. Negative Regulation
25
Allosteric Effectors
Binding can also be required for binding of
repressor (e.g. Trp) or can block an activator.
26
(?) ???????

• ??????????
• ????????????
• ???????????

27
1.?????(lac operon)

• ????
• ??????Z?Y?A,????ß-?????(ß-galactosidase)???(permea
  se)?????????(galactoside acetylase)
• ??????????(P)???????(O)
• ?????????CAP??????

28
Organization of Lac Operon and LacI
promoter
29
Regulation of Gene Expression
???
(?????????)
30
(No Transcript)
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Adenylate cyclase and CAP mediate glucose
repression of Lac
Adenylate cyclase (AC) is an enzyme that
synthesizes cyclic AMP (cAMP) from ATP
High glucose ? adenylate cyclase is inhibited
(indirectly, via a catabolic product) Therefore
cAMP levels are LOW
Absence of glucose ? adenylate cyclase is NOT
repressed Therefore cAMP levels are HIGH
cAMP forms a complex with the CAP protein, which
allows it to then bind to the CAP site upstream
of the Lac operon. Binding of the CAP protein is
required to allow RNA polymerase to bind to the
lac promoter and turn on transcription. In the
absence of CAP binding, there is no (or very
little) transcription of the lactose operon, even
in the presence of lactose.
32
CAP Binding Bends DNAv
This DNA bending results in more efficient RNA
polymerase binding
33
CAP mediates glucose repression of Lac
Promotes transcription
34
????

• I??????????,????????,?????????,???????????????????
  ,?????????,?ß-??????????????,???????(inducer)?????
  ??,????????????,???????

35
Four States of the Lac Operon
LacI
Lactose Glucose
-
- -
CAP-cAMP
-

36
2.???????(ara operon)

• ????
• ???? B?A?D,???????(isomerase)???(kinase)????(epi
  merase),?????????5-?????
• ??? ????(P)????(I)?????(O)??

37
CAP
38
????

• C???????,??????AraC, AraC???????,???araO1?araO2,??
  ?????????AraC????,???araI?,???????ara??????????,C
  AP???????????

39
The Arabinose Operon
Arabinose present, Glucose absent, operon ON
No Arabinose present, operon OFF
This loop prevents RNA transcription (NOT true
for all loops)
40
????

• ????,?????????
• ????,???????
• ????,???????

41
3.??????(trp operon)

• ????
• E.coli??????????????E?D?C?B?A???????,???????,
• ?????????(P)?????(O)??
• R????????

42
(No Transcript)
43
Genomic Organization of the Trp Operon
44
????

• ?????????????????????E?????O???L????L???????????14
  ????,??????????????,??????????????????????????????
  ?????
• ????
• ???????????,?????????

45
Control of Gene Expression in the Trp Operon

1. The enzyme catalyzing the first step in the
   pathway is inhibited by Trp (feedback control).
2. In the presence of Trp, a repressor protein binds
   to an operator upstream of the Trp operon and
   shuts off transcription
3. Attenuation. There is a 160 base pair region in
   the Trp mRNA that causes transcription to
   terminate prematurely if Trp is present.

46
Trranscriptional Control
47
Attenuation Control
48
? ???????

• SD??(Shine-Dalgarno sequence)
• ????????mRNA??????,?????????
• SD????????????????SD?????,???????
• mRNA??????SD?????

49

• mRNA????
• mRNA?????????????????
• mRNA??????????(??????????)??

50

• ????????????
• ????? 50??????????????????????mRNA??????????????,
  ????????
• ??????RF2??????? ?25??????315??????UGAC??RF2???

51

• ???RNA?????
• ??????????? mRNA?????RNA(mRNA interfering
  complementary RNA,micRNA)
• ?????????? ???RNA???????????????????

52
??? ?????????
53
? DNA?????

• ????? ??????????,???
• ????
• ???? ???????????,??????????

54

• DNA??? ???????????
• ????????????????????????
• 5'???????????????CG????????
• DNase?????????????
• ??????? ????DNA?????
• ????????????DNA,?????????????

55
? ???????

• (?) ???????????????RNA???????????DNA??,????????
  ???(transcription factor,TF)?DNA??????-DNA???
• TFIID??TATA?
• RNA?????TF?D,????????
• ??TF?RNA???????????

56
(?)??????

• ??????????DNA(8-15bp)????
• ???????(???)???(???)
• ???????DNA???,?????,?????????

57
DNA Structure Major and Minor Grooves
58
DNA???(DNA-binding domain)

• ????(Zinc finger motif)
• ?????(Homodomain)
• ?????(Leucine zipper)
• ??-?-??(Helix-loop-helix structure)
• ??a ??(Alkaline a-helix)

59
Zinc Finger Motif
60
Helix-Turn-Helix Motif
61
Leucine Zipper
62
Leucine Zipper
Zipper every 7th residue is a Leu ? Hydrophobic
interface
63
H-Bonding in a Protein-DNA Interaction
64
???????(transcriptional activation domain)

• ??a-?????(acidic a helix domain)
• ?????????(glutamine-rich domain)
• ????????(proline-rich domain)

65
(?)???????

• ???????????
• ????? ???????,????
• ???? ????????,???
• ???? ????
• ??????????? ?????????

66

• ??????????????
• ???????????
• ??
• ??
• ??
• Oozing
• ??????????????
• ???????(conbinatorial gene regulation)????????????
  ?????

67
? ????????

• ??????????
• ?????????
• ????(alternative splicing)exon,intron???????mRNA?
  ?????
• Exon??,intron??,??exon,??????
• mRNA?????

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(No Transcript)
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(No Transcript)
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71

• Recent genome-wide analyses of alternative
  splicing indicate that 4060 of human genes have
  alternativesplice forms, suggesting that
  alternative splicing is one of the most
  significant components of the functional
  complexity of the human genome. Here we review
  these recent results from bioinformatics studies,
  assess their reliability and consider the impact
  of alternative splicing on biological functions.
  Although the big picture of alternative
  splicing that is emerging from genomics is
  exciting, there are many challenges.
  High-throughput experimental verification of
  alternative splice forms, functional
  characterization, and regulation of alternative
  splicing are key directions for research. We
  recommend a community-based effort to discover
  and characterize alternative splice forms
  comprehensively throughout the human genome.

-------A genomic view of alternative
splicing Barmak Modrek Christopher Lee nature
genetics volume 30 january 2002
72
? ???????

• ???????
• ?????????
• ???????????
• AUG??????
• mRNA5'????????????
• mRNA?????
• ???RNA????????

73
? ????????

• ???????
• ???????????
• ?????????????

74
(No Transcript)
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(No Transcript)
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(No Transcript)
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(No Transcript)
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(No Transcript)
79
? ???????????