Post on 02-Sep-2018
TranscriptionandPostTranscriptModification
YouShouldBeAbleTo…
1. Describetranscription.2. Compareandcontrasteukaryotic+
prokaryotictranscription.3. ExplainmRNAprocessingineukaryotes.4. Describehowtranscriptioncanbecontrolled
ineukaryotes.
CentralDogma
DNA
mRNA
mRNA
protein
ribosome
Transcription
Translation
DNA
mRNA
RNAPolymeraseII
Transcription
1. RNAPolymeraseIIattachestoDNA(initiation).2. RNAPolymeraseIImakesanRNAstrand(elongation).3. RNAPolymerasedetachesfromDNA(termination).
Prokaryotes
geneàß “upstream”ofgene
EukaryotesPromoterregion
Eukaryotes
1. RNAPolymeraseIIattachestoDNA(initiation).2. RNAPolymeraseIImakesanRNAstrand(elongation).
3. RNAPolymerasedetachesfromDNA(termination).
Prok:RNAPolII+SigmaFactor….atthe-35boxand-10boxEuk:RNAPolII+Transcr.Factors…atthe-30box,akathe“TATAbox”
Figure17.1
RNA
Templatestrand
Hydrogen bonds formbetween complementarybase pairs
DNA template
RNA
Phosphodiesterlinkage is formed by RNA polymeraseafter base pairingoccurs
DNANon-template (coding) strand
Incoming NTP(monomer)
© 2017 Pearson Education, Inc.
1. RNAPolymeraseIIattachestoDNA(initiation).2. RNAPolymeraseIImakesanRNAstrand(elongation).
3. RNAPolymerasedetachesfromDNA(termination).
Prok:RNAPolII+SigmaFactor….atthe-35boxand-10boxEuk:RNAPolII+Transcr.Factors…atthe-30box,akathe“TATAbox”
Fig.17-9
TranscriptionTerminationinEukaryotes:
• ThesequenceAAUAAA• SignalsfortheRNAtranscripttobecleaved.
1. RNAPolymeraseIIattachestoDNA(initiation).2. RNAPolymeraseIImakesanRNAstrand(elongation).
3. RNAPolymerasedetachesfromDNA(termination).
Prok:RNAPolII+SigmaFactor….atthe-35boxand-10boxEuk:RNAPolII+Transcr.Factors…atthe-30box,akathe“TATAbox”
Prok:RNAHairpinformsEuk:Terminationsequence+Enzymes
CentralDogma
DNA
mRNA
mRNA
Protein
Ribosome
Transcription
Translation
Eukaryotesà
TheRNATranscript
Eukaryotesà
TheRNATranscript
IntronsandExons
Intron:AregionofaeukaryoticgenethatistranscribedintoRNAbutislaterremovedbyaspliceosome.
Exon:AtranscribedregionofaeukaryoticgeneorregionofaprimarytranscriptthatisretainedinmatureRNA.
AnatomyofaEukaryoticGene
Transcription
IntronsCutOut
CapandTailAdded
Primarytranscript
MaturemRNA
Fig.17-11-3RNAtranscript(pre-mRNA)
Exon1 Exon2Intron
ProteinsnRNA
snRNPs
Otherproteins
5¢
5¢
Spliceosome
Spliceosomecomponents
Cut-outintronmRNA
Exon1 Exon25¢
CentralDogma
DNA
mRNA
mRNA
protein
ribosome
MaturemRNA
Fig.17-9
Protein-codingsegment Polyadenylationsignal3’
3’UTR5’UTR
5’
5’Cap Startcodon Stopcodon Poly-Atail
G P PP AAUAAA AAA AAA…
thisregionwastranscribed
butonlythisregiongetstranslated
Humanshave~20,000genesand>100,000typesofproteins.
• HowisthispossibleifDNAàmRNAàProtein?
Fig.17-11-2RNAtranscript(pre-mRNA)
Exon1 Exon2Intron
ProteinsnRNA
snRNPs
Otherproteins
5¢
Spliceosome
AlternativeGeneSplicing
AlternativeGeneSplicing
Spliceosome
Primarytranscript
AlternativeGeneSplicing
Fig.17-3b-3
(b)Eukaryoticcell
TRANSCRIPTION
Nuclearenvelope
DNA
Pre-mRNARNAPROCESSING
mRNA
TRANSLATION Ribosome
Polypeptide
RegulationofGeneExpression
Eukaryotes
RegulationofGeneExpression
Thereareatleast300differentkindsofcellsinthehumanbody.
MostofthemhaveidenticalDNA.
Inorderfordifferenttypescellstoproducedifferenttypesofproteins,theyneedto
producedifferenttypesofmRNA.
Campbell8e,Fig.18.9
Campbell8e,Fig.18.10
ControllingGeneExpression:EnhancersandActivators
§ Provideawaytoturnonspecificgenesinspecificcells
§ Differentgeneshavedifferentenhancers
§ Differentcellshavedifferentactivators
Campbell8e,Fig.18.10
ControllingGeneExpression:EnhancersandActivators
§ Tissue- andcell-typespecificgeneexpression
§ Livercellsmakealbumin,butnotcrystallin
§ Lenscellsmakecrystallin,butnotalbumin
Campbell8e,Fig.18.10
ControllingGeneExpression:EnhancersandActivators
- Differentgeneshavedifferentenhancers.
- Differentcelltypeshavedifferentactivators.
YouShouldBeAbleTo…
1. Describetranscription.2. Compareandcontrasteukaryotic+
prokaryotictranscription.3. ExplainmRNAprocessingineukaryotes.4. Describehowtranscriptioncanbecontrolled
ineukaryotes.
LB145