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CMB2001 > RNA degradation > Flashcards

RNA degradation Flashcards

1
Q

why is RNA degradation important

A

damaged mRNA, incorrectly transcribed/processed mRNA and control of gene expression

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2
Q

where is casein mRNA expressed

A

mammary gland

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3
Q

Casein mRNA increase _ on stimulation by _

A

70 fold
prolactin

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4
Q

what is prolactin

A

hormone promoting milk production

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5
Q

Despite the massive increase in mRNA, transcription only increases 2 fold. How?

A

half life increase (40 fold), polyA tail length increases & 3’ UTR of RNA binds to proteins which aids stabilisation

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6
Q

Eukaryotic mRNAs is _ during translation

A

Circular

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7
Q

how does mRNA being circular aid in mRNA integrity being monitors

A

it will not be circular if it has lost cap or poly (A)

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8
Q

at the 5’ end what is it suggested about the ribsomes

A

recycled

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9
Q

Closed lopp must be broken before _ can gain access

A

exonucleases

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10
Q

what are the 2 decapping enzymes

A

DCP1 & 2

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11
Q

what are the 3 endonucleases enzymes

A

Argonaute, Swt1 and Smg6

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12
Q

what is the deadenylases

A

Ccr/Not complex

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13
Q

what are the enzymes that initiate the breakdown of the RNA

A
  • Decapping enzymes
  • endonucleases
  • deadenylases
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14
Q

what is phase II mRNA degradation

A

5’ to 3’ & 3’ to 5’ exonuclease

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15
Q

what is the exosome

A

the main 3’to5’ exonuclease in the cell involved in RNA turnover and processing

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16
Q

what are the 2 nuclease activities involved in the exosome

A

RRP6 & RRP44

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17
Q

what is the function XRN1

A

5’ to 3’ exonuclease Involved in RNA turnover and processing & transcription termination

18
Q

When does XRN1 function

A

decapping of the mRNA

19
Q

what are the two types of decay

A

deadenylation dependent and independent

20
Q

what stimulates the deadenylase complex

A
  • AU-rich element or ARE
  • Nosense codon
  • c-fos major coding determinant
  • miRNA
21
Q

how is Rps28B regulated

A

auto-regulation - negative feedback where it binds to its own message

22
Q

what works with Rps28B and what does it do ?

A

Edc3 which is one of several activators of decapping enzymes

23
Q

give an example of a nuclease targeting specific substrates

A

PMR1 cleaves albumin mRNA

24
Q

what is NMD

A

Nonsense-Mediated Decay

25
Q

what fraction of inherited disorders are causes by nonsense/frameshift mutatations which causes premature atop codons

A

1/3

26
Q

what error can be causes by a premature stop codon

A

Transcription, Splicing, Editing, Polyadenylation, Mutations

27
Q

what is the distance between Exon 3 and Exon4/STOP for mRNA to be a potential NMD target

A

greater than 55 nucleotides

28
Q

what is the process by which NMD works called

A

surveillance

29
Q

how does NMD work

A

In the first round of translation, EJCs are removed from the
mRNA by the ribosome.
When ribosomes reach the PTC, an EJC remains, specific factors that are part of
the EJC or are recruited to it interact with the RNA degradation
machiner

30
Q

what are the specific factors that are either part of the EJC or interact with it called

A

UPF proteins

31
Q

what are EJCs

A

Exon junction complexes

32
Q

what are RNAi

A

RNA interference

33
Q

what are siRNA

A

small inhibitory RNA

34
Q

what is miRNA

A

micro RNA

35
Q

what is RISC

A

RNA induced silencing complex

36
Q

what are the difference between siRNA and miRNA (1)

A

Si = perfect complimentary to target RNA
mi = imperfect complimentary

37
Q

what are the difference between siRNA and miRNA (2)

A

Si = mainly viral defence mechanism
mi = key gene reg mechanism

38
Q

what are the difference between siRNA and miRNA (3)

A

si= leads to degradation of target RNA
mi = leads to block in translation

39
Q

both miRNA and siRNA duplex do what to mRNA

A

unwind the RNA

40
Q

during embryonic development, 3’ UTR frequenctly gets _

A

longer

41
Q

mRNA in proliferating cells tend to have _ 3’UTRs

A

shorter

CMB2001 (11 decks)

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