Biol3015 transcriptional control and genetic diseases
Subjects
transcriptional control
genetic disease
genes
regulation
transcription
tata
promotors
mediators
enhancers
silencers
insulators
regulation of gene expression
Written for
University of Southampton (UOS)
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Transcriptional control and genetic diseases
Transcriptional control
The complexity of the eukaryotic system
RNA Polymerase I transcribes ribosomal RNA genes
RNA Polymerase II transcribes Protein coding genes miRNAs – non coding RNAs
RNA polymerase III transcribes tRNA genes
Core promotor
Transcriptions starts at +1 shown by an arrow
Downstream is positive, upstream is negative
Inr (initiator elements)
Transcription usually starts at an A flanked by pyrimidine rich sequence
This region is called the initiator
YY A NYAYY
YY – pyramidine
A start base
The TATA box
Sequence RNApol
Transcription about 30 bases downstream
The conserved C-terminal domain of TBP binds to TATA-box DNA
TATA-binding protein = TBP
Stepwise assembly of Pol II transcription-initiation complex
TFIID
Binds first
Binds to TATA
800KD in size
TBP – TATA box binder – recognises box – 30KD
When binding DNA bends at 90o angle
TAFs – 11 of them – 18-250 KD – associated factors
TFIIA
Binds next
Stabalises reaction of TFIID with DNA
TFIIB
Binds next
Binds solo through protein interactions
Recruits RNApol to DNA
RNApol II
Comes with TFIIF
TFIIE
ATPase – provides energy
TFIIH
Helicase
A pre-initiation complex (PIC) is assembled
DNA strands split
Initiation of transcription
, TATA less promoters
Only 25% of genes have TATA box
Other 75% have an INR and DPE
DPE
DPE is a downstream promoter element
DPE have the sequence AGAC
Located +28 and +32
TFII I recognises DPE – transcription starts
Genes with TATA box
Single start site
Highly controlled genes
DPE genes
Multiple start sites
Constitutively expressed genes
Transcription initiation at eukaryotic protein-coding genes
# of subunits Activity
RNA pol II 12 RNA synthesis
General TX factors
TFIID 9 Promoter recognition
TFIIB 1
TFIIE 2
TFIIF 2
TFIIH 9 Helicase
Upstream Sequence Elements (USEs)
MyoD – activates gene in muscle cells – binds to GGGCGG
PIC directs only a low level of transcription
Transcription is enhanced by the binding of transcription factors to sites upstream,
of the TATA/Inr
Transcription factors that confer general transcription
SP1
GGGCGG
Transcription factors that confer tissue specific transcription
MyoD – CANNTG - Muscle Specific
Oct-2 – ATGCAAT - B cell specific
Transcription factors that confer inducible transcription
CREB - T/GT/ACGTCA - cAMP
Estrogen receptor – AGGTCANNNTGACCT - Estrogen
Regulatory sequences that act at a distance
1. Enhancers
2. Silencers
3. Insulators
4. LCRs
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