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Gene regulation > Therapeutic potential of regulatory RNAs > Flashcards

Therapeutic potential of regulatory RNAs Flashcards

1
Q

What can siRNAs do to a mutated genes mRNA?

A

“knock-down” the mRNA

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2
Q

Which body cells possess the machinery which constitutes a functional siRNA/miRNA pathway?

A

All body cells

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3
Q

What takes up siRNAs?

A

RISC complex (RNA Induced Silencing Complex)

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4
Q

What does the RISC complex use siRNA for?

A

A scanning target for mRNA

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5
Q

What happens to mRNA with sequence complementarity to siRNA?

A

It is bound by the siRNA

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6
Q

What happens to mRNA once bound to siRNA?

A

It is degraded by enzymatic components of the RISC complex

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7
Q

What kind of organisms use siRNA/RISC to combat viral infection?

A

Plants and other lower organisms

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8
Q

What do plants and other lower organisms use RISC for?

A

A means of combating viral infection

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9
Q

How is siRNA manipulated by scientists?

A

an siRNA that has sequence complementarity to any mRNA of interest is designed and this can be used to knock down mRNA

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10
Q

What is an example of a type of gene that siRNA can be used to target?

A

Oncogenes

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11
Q

What is the philadelphia chromosome?

A

A fusion of chromosome 9 and 21

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12
Q

What is the issue with the philadelphia chromosome?

A

Where the chromosomes fuse creates a BCR-ABL oncogene which is cancerous

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13
Q

What is caused by the BCR-ABL oncogene?

A

Leukaemia

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14
Q

How can siRNA help therapeutically with leukaemia?

A

siRNA against fusion point between BCR and ABL gene is designed,

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15
Q

Why is the siRNA against leukaemia on the philadelphia chromosome targeted specifically against the fusion point of the BCR and ABL gene?

A

So it doesn’t target any normal BCR or ABL genes that aren’t fused

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16
Q

Where is the BCR gene found?

A

Chromosome 22

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17
Q

Where is the ABL gene found?

A

Chromosome 9

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18
Q

Why is siRNA a useful way of targeting viral infections?

A

siRNA can be quickly redesigned to keep up with mutations of the virus

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19
Q

Why can siRNAs not be given orally?

A

The acid contents in the stomach degrades siRNAs

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20
Q

How must siRNAs be adminitered?

A

Intravenously

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21
Q

What is an issue with administering siRNAs intravenously?

A

There are exonucleases in the blood that will recognise the siRNAs as foreign and start to degrade them, as well as immune cells that do the same thing

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22
Q

Issue with siRNA size?

A

They are rapidly filtered by the kidneys and so cleared

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23
Q

Issue with siRNAs and plasma membrane?

A

They have an overall -ve charge (RNA phosphate backbone) so they can not cross cell membranes

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24
Q

How is the immune response to siRNAs combated?

A

You can change the RNA structure that repels the immune system and exonucleases

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25
Q

What edits are done to siRNA to prevent exonucleases and the immune system from attacking?

A

Add a 2’ O-methyl group instead of a hydroxyl group, phosphorothionate linkages

26
Q

In what direction do most exonucleases act?

A

5’ to 3’

27
Q

How does adding a 2’ O-methyl group to siRNA prevent exonuclease degradation?

A

Recognition from the exonuclease is prevented

28
Q

What do phosphorothioate linkages replace?

A

Phosphodiester bonds

29
Q

Difference between phosphodiester bonds and phosphorothioate bond?

A

Oxygen atom is changed to a sulfur

30
Q

What are locked nucleic acids?

A

Altered structures of DNA or RNA, not strictly DNA or RNA–> they are synthetic nucleic acids

31
Q

Features of locked nucleic acids?

A

Oxygen present at the 2’ carbon which is crosslinked to carbon at position 4

32
Q

Why are locked nucleic acids used?

A

Exonucleases and the immune system wont recognise them

33
Q

Benefit of locked nucleic acids other than not being recognised?

A

They bind more potently to their targets than siRNAs do

34
Q

How are siRNAs helped to cross the cell membrane?

A

They are encased in lipid nanoparticles

35
Q

What types of lipids make up lipid nanoparticles?

A

Neutral lipids and cationic lipids

36
Q

How is the -ve charge of siRNAs neutralised?

A

Cationic lipids are +vely charged

37
Q

How is the molecular weight of siRNAs increased?

A

Polyethylene groups

38
Q

Which two things to lipid nanoparticles do that helps siRNAs?

A

Remove the -ve charge and increase their molecular weight

39
Q

When are lipid nanoparticles used?

A

When a systematic delivery is wanted

40
Q

What type of delivery is used when you want to deliver siRNAs to a specific organ or cell type?

A

Targeted delivery

41
Q

What encases siRNAs in targeted delivery?

A

Targeted cationic polymers

42
Q

What make up targeted cationic polymers?

A

polycations, polyethylene groups, targeting ligand

43
Q

What is the targeting ligand specific to in targeted delivery?

A

A receptor on the surface of the cell/organ you are aiming for

44
Q

How is the polymer nanoparticle taken up in targeted delivery?

A

Receptor mediated endocytosis

45
Q

Issues with receptor mediated endocytosis?

A

The molecules are not readily released from the endosome

46
Q

What happens if the contents of an endosome is not readily released?

A

They get transferred to a lysosome where they are degraded

47
Q

What is endosomal escape?

A

The release of something from an endosome

48
Q

What is used to aid endosomal escape?

A

Using proton sponge groups

49
Q

Where are proton sponge groups added?

A

siRNA complex

50
Q

What do proton sponge groups do?

A

Cause protons to be pumped into the endosome, eventually causing it to burst

51
Q

Examples of successful in vivo trials?

A

Haemophilia, ebola

52
Q

What causes hemophilia?

A

mutations in clotting factors, so they are not produced–> persistent bleeding

53
Q

Where are clotting factors produced and what with?

A

In the liver, with anticoagulants

54
Q

Method of targeting hemophilia with siRNAs?

A

Targeting anti clotting factors, restoring the balance between clotting factors and bleeding factors

55
Q

Successful siRNA of hemophilia?

A

Attaching GalNAc groups (ligands) to antithrombin siRNAs

56
Q

What do GalNAc groups do?

A

Bind to proteins found on the surface of liver cells

57
Q

Which ligand does GalNAc attach to?

A

ASGPR receptor

58
Q

Result of GalNAc siRNA?

A

Reduced levels of antithrombin being produced

59
Q

How was siRNA used against ebola?

A

siRNA designed against murkona strain of ebola

60
Q

What kind of delivery was used for the ebola siRNA?

A

LMP (systematic delivery)

61
Q

Which animals were used to test the ebola siRNA and did it work?

A

Monkeys, and yes

Gene regulation (12 decks)

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