Gene Regulation II Flashcards
What are the core components which regulate eukaryotic transcription
RNA polymerase (RNA Pol II)
General TFs (assemble promoter sequence to start transcription)
What are the regulatory components of eukaryotic transcription
Regulatory TFs
Interact with regulatory sequence (enhancers and silencers transcribed away from gene)
Mediator complex
Nucelosome remodelers
Histone modifiers
Three ways in which regulatory TFs act to control transcription
1) facilitate assembly of core components at the promoter via mediator complex
2) change accessibility of DNA by recruting chromatin remodelling proteins
3) recruiting histone modification enzymes adding or removing activation/repression markers
What does each eukaryotic gene have
Characteristic regulatory sequences which are recognised by different regulatory TFs
What is needed for full activation of transcription
More than one TF
3 ways to control the availability of TFs
1) expression level
2) post transcriptional protein modification (phosphorylation)
3) cellular localisation
What controls the expression of regulatory TFs in the spinal cord (development)
Shh
Floorplate and notochord secrete Shh
What does Shh downregulate
The homeobox
Signalling which induces gene expression
PKA and cAMP
PLC/IP3/DAG (GPCR slower than ionotropic)
Ras-RAF
Ca-Cam
What does pre-MRNA contain
Introns (must be removed by splicing)
What controls splicing (post transcriptional modification)
Specialised nucleotide sequences
Core splicing machinery
Regulatory splicing factors
ESE & ISE
Exonic and intronic splicing enhancers
Sequences which recruit regulatory splicing factors activating splicing
ESS and ISS
Inhibit splicing
Activators and repressors
RNA binding proteins from the SR family = activators
RNA binding proteins from the hnRNP = repressors
5’ splice site, 3’ splice site, branching point
Intronic sequences
Recognised by: U1 snRP, U2AF (forms contact with polypyrimidine tract preceding the 3’ splice site), U2 snRP
Protein which regulate splicing in the nervous system
nPTB
What is alternative splicing
Non uniform inclusion of exons and removal of introns
How many intron containing genes form more than one spliced mRNA isoform
~90%
Splicing of src kinase pre mRNA
Non neuronal cells contain PTB (downregulated in neurons)
Neurons contain hnRNP (repressor of splicing)
How is alternative splicing regulated in neurons
Depolarisation
NMDAR and L type calcium channel increase cellular calcium concentrations
hnRNP is phosphorylated by CaMKIV
Negative feedback decreases activity of NMDAR so less calcium entry
Role of Dscam1 gene encoded in drosophila
Surface protein necessary for proper development of axons and dendrites in fruit fly neurons
Dscam1 isoform
4 arrays of mutually exclusive exons allow dscam1 protein isoform (38,016 combination)
Enough isoforms are needed for correct neural circuits
