Transcription II Flashcards
What’s the difference between prokaryotes and eukaryotes?
Non vs membrane bound nucleus
RNA polymerase divides into I,II,III. Describe RNA polymerase I
Pre rRNA - Ribosome components, protein synthesis
Describe RNA polymerase II
mRNA, snRNA, siRNA - All protein-coding genes, RNA splicing, repression, translation control
Describe RNA polymerase III
Protein synthesis, Ribosome component, RNA splicing, insertion of peptides into ER
Describe mRNA
Codes for proteins
Describe rRNA
Form core of ribosomes structure, catalyse protein synthesis
Describe (micro) miRNA
Regulate gene expression
Describe tRNA
Adaptors between mRNA/AA during protein synthesis
Describe other non-coding RNA
Used in RNA splicing, gene regulation, telomere maintenance
Describe the role of transcription factor II (TFIIs)
Recognise the promoter (specifically for RNA polymerase II)
Describe what RNA polymerase binds to
Binds and forms transcription initiation complex
Describe the CAAT and GC box, including the TATA box
CAAT and GC box found in many promoters, but TATA box needed for initiation
(TATA found upstream)
Describe the formation of the pre-initiation complex
TFs fall into place on DNA template with each one further stabilizing the preinitiation complex
Describe the steps in Transcription - Initiation
- Polymerase binds to promoter sequence in DNA (close complex)
- Polymerase opens DNA near transcription start site forming bubble (open complex)
- Polymerase catalyses phosphodiester linkage of 2 initial nucleotides
- Polymerase moves 3’-5’ along template strand adding nucleotides to growing RNA (Rate of elongation - 1000 nuc/min at 37degs)
- Transcription stop site, polymerase releases completed RNA and dissociates from DNA
What does RNA polymerase II transcribe?
RNA poly II transcribes poly-adenylation sequence at end of gene (AAUAAA), then continues for 10-35 nuc, proteins recognise sequence, cut RNA free
Describe how the transcription initiation is controlled
Using activators, Enhancers/Silencers, Coactivators, Repressors, Basal transcription factors
Describe activators
Bind to genes on enhancers, speed up rate of transcription
Describe enhancers/silencers
Affect efficiency of transcription, needed for initiation to occur
Describe coactivators
Adapter molecules that integrate signals from activators/repressors
Describe repressors
Bind to selected sets of genes and silencers, slowing transcription
Describe basal transcription factors
Position RNA poly at start of transcription, initiate process
Where is the CAP and Poly A tail found?
Describe the steps after these additions
5’ CAP and poly A at 3’ end
mRNA from degradation
Spliceosome removes introns to produce mature mRNA
Exons joined together
What are the 2 functions of a cap?
Protects RNA from degradation
Needed for translation of mRNA
What is the GU-AG rule?
Each intron cut at each end, almost always have GU at 5’/AG at 3’ end
Introns removed from primary transcript while RNA still being synthesised and after cap is added, but before transcript is transported into cytoplasm
