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Control Of Gene Expression > Translation And Regulation > Flashcards

Translation And Regulation Flashcards

1
Q

What makes up eukaryotic ribosomes

A 
80s ribosome 
40 ss, 60 ls.  
18s rRNA,28s rRNA, 5.8,5 
LS has 50 proteins 
Ss has 33 proteins
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2
Q

What is the catalytic subunit of ribosome

A

Rna

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3
Q

What gets transferred to trnas via trna synthetase

A

Amino acid + adenosine tp (2ppi lost for energy)

= amino adenylate = amino acyl trna

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4
Q

Why is ribosomal rna needed

A

Peptide bond formation is unfavourable

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5
Q

What are the 3 sites on the 40s subunit

A

EPA
Exit
Polypeptide chain site
Amino acyl trna bs

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6
Q

What sequence is scanned by the ribosome around the aug start

A

Kozak consensus

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7
Q

Does small subunit 40 bind to cap for initiation

A

Yes

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8
Q

What needs to happen structurally to mrna for initiation

A

Circularisation by bringing cap and poly a together

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9
Q

What complex is responsible for initiation

A

Eif4 complex (g,e,a)

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10
Q

What eif4 binds to the cap

A

Eif4 E

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11
Q

What does eif4 G bind

A

Eif4 A, 3 and poly A binding proteins and E (circularising mrna)

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12
Q

What does eif4 A have

A

ATPase and rna helicase

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13
Q

What is the eif2 complex

A

Eif2 gtp, attached to trna met (start trna)

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14
Q

What does eif2 complex associate with first in translation

A

43s pic

Recycled 40s subunit, eif 1a,1 and 3

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15
Q

Once the 43s is attached to the eif2 trna complex. What attaches

A

The eif4 E binds to cap, eif4G binds to pabp,3, and E causing circularisation

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16
Q

Once the 43s binds with the eif4 complex around the cap, what happens

A

Can scan the start codon and kozak

17
Q

What happens when start codon is scanned

A

Eif2 gtp is hydrolysed, the 43s binds with the eif4 complex and eif2complex.
= 48s initiation complex
Trna met can join via anticodon

18
Q

What allows the 60s subunit to bind

A

Eif5b GTP hydrolysis. This occurs when the 48s initation complex is attached to start codon

19
Q

What happens to eif when 60s binds

A

All leave at different times

20
Q

What allows elongation by bringing a new amino acyl trna to the A site

A

Ef G 1a and gtp hydrolysis

Then allows translocation

21
Q

What is peptide forming called

A

Peptides transferase reaction (via rna catalism )

22
Q

Which release factor binds stop codon in A site

A

Erf1

23
Q

Which release fsctor cleaves peptide chain from trna

A

Erf3 gtp hydrolysis

24
Q

after erf3 hydrolysis, what is released and recycled

A

Ribosomes, trna released

The 40s stays with 1,1a and 3 forming the 43s pic

25
Q

How is EIF2 used to regulate translation

A

It is phosphorylsted which stops it’s action - means no gtp hydrolysis of eif2 = no start codon recognition and no 48s initation complex

26
Q

When is eif2 inactivated

A

Eg due to amino acid shortage or cell stress

27
Q

What dephosphorylates eif2 activating it

A

Growth factors

28
Q

How can eif2 regulation be used to switch only mrna to do with stress eg heat shock on for translation

A

Via distinctive elements on mrna which identifies them

29
Q

How does level of irons impact

A

They regulate expression of transporters of iron or storage of iron if too high

30
Q

What are UTRs

A

Untranslated regions on mrna

5’ Utr Is between cap and start codon (binding blocks ribosome scanning)

3’ is between stop codon and poly A (for stability)

31
Q

What happens in low iron levels

A

Mrna for transporters is up regulated to get more iron

This is via IRP1 binding to the 3’ utr for stability = more expression

IRP1 binds to 5’ utr on storage mrna = blocked translation

32
Q

What does IRP1 bind to on rnas

A

IREs

33
Q

In high iron levels, the iron binds to IRP1, how does this have effect on storage mrna

A

It means IRP1 can’t block translation of storage mrna because can’t bind to 5’ utr = translated

Also means it can’t stabilise at 3’ utr for the transporter mrna = unstable and degraded

34
Q

What does bi functionality of IRP1 mean

A

When it’s bound to iron it changes it’s role to a c aconitase

Control Of Gene Expression (13 decks)

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