Regulation Of Transcription 1 Flashcards
What does RNA world mean
Rna could self replicate and were catalytic to form proteins
What is rnp world
Translation into proteins from rna
Rinonucleo proteins
What is Luca
Last common ancestor that used DNA as genetic info store
Is all rna translated
No but all rna modified
What is the diff between euk and pro transcription and translation
Euk mrna needs to be exported to cytosol where ribosomes are
They are specially and time different
What do viruses target
Regulation processes Eg txn regulation, export regulation or translation regulation
Are 5’ m7g cap and poly a added post transcription
Yes. They aren’t encoded by genome
Which 4 processes happen to form mrna from
Pre mrna
Capping splicing poly adenylation and editing
What recruits factors for the 4 processes of mrna production Eg splicing
The CTD of rna pol II
Which rnas are capped
All transcribed by rna pol II. Ie mrna, snrna and mirna
How is a 5’ cap added
A guanosine with a ribose and guanine is added by 5’ phosphate attached to the ribose
The 5’ phosphate is the from the rntp terminally at 5’ which forms an unusual 5’ to 5’ between ribose then 3 P then another ribose at 5’ instead of 3’
The guanine N7 is then methylated (ch3) to form a cap
How does the cap maintain mrna stability
It stops action of 5’ to 3’ exonucleases
Proteins can bind via the methylation of guanosine at n7. What are they
Splicing factors
Export factors
Translation factors
Give an example of an export factor that can bind to the m7g cap
Cbp80/20
Which fsctor binds to cap in translation
Eif4
What does splicing introduce in mrna
Open reading frames by removing introns
Do most genes have introns
Yes but vary in size
Which gene has largest introns
Dystrophin
What are the 3 conserved sequences for intron and exon boundaries
5’ splice site
Branch site (A)
3’ oh splice site
Which splice site has most pyrimidines Eg c or t (y)
3’ ss
What does splicing reserved sequences recruit
Spliceosome
How many reactions and what type is splicing
2 trans esterification reactions
What is the first trans esterification reaction in splicing
5’ splice site is cleaved and joins the A branch site to form a lariat loop
What happens in the second trans esterification reaction
3’ splice site is cut removing the lariat which is degraded
Ligation of the 2 exons occurs
What is the spliceosome
Enzyme/ protein complex which gathers on each intron and uses atp
What 4 things make up spliceosome
ATPase
Gtpase
Rna binding proteins (RBP)
Sn rnps (small nuclear ribonucleoproteins)
What makes up snRNPs which are the catalytic unit of spliceosome
1 sm protein
1 sn rna (non coding)
What sn rna in sn rnps base pairs with the 5’ splice site and cleaves it
U1
Which sn rna base pairs with branch site Ain splicing
U2
Which sequence is conserved in all sn rnas (u1,2,4,5,6)
Sm protein binding site
Which autoimmune disease forms anti sm antibodies which react with the sm proteins in snRNPs
Lupus LSE
Before the 2 step trans esterification what happens to pre mrna
U1 will bind to 5’ ss
U2 will bind to branch site
Forms A complex
Then u4,5,6 also bind onto the pre mrna
Forms b complex
At what point does step 1 trans esterification occur
When u1 and u4 are released leaving only u2,5,6 (B* complex)
The lariat loops forms as 5’ ss is cleaved
What complex are the sn rnas in when step 2 of trans esterification occurs
C complex u2,5,6
The 3’ ss is cut releasing the lariat with the sn rnas
The exons are ligated
How can splicing form different protein isoforms from 1 gene
Alternative splicing
Which 3 things can be mutated in splicing
The introns
The sn rnps (can’t slice efficiently)
Splicing factors
Which sequence conserved during mrna transcription in 90% triggers poly adenylation
AAuAAA
What region is found downstream of the poly A site
A g/U rich site
What binds to the AAUAAA sequence and what does it bring to cleave the mrna to stop transcription
CPSF - cleavage and polyadenylation stimulating factor
Brings endonuclease
What binds to the G/U rich downstream sequence after poly a site
CSTF - cleavage stimulatory factor
What does CSTF cleavage stimulatory factor activate at the g/u rich downstream of poly A site
CF 1 and 2 (cleavage factor 1 and 2)
Which enzyme allows encorporation of adenine residues at 3’ end
Poly a polymerase
What 3 things does 250 poly A addition do via binding of proteins
Stabilise mrna from exonucleases (like cap) Enhance translation (like cap does) Allow exportation (like cap does)
