Non Coding Rna

Question 1

RNA Interference/silencing

Answer 1

-naturally occurring mechanism
-occurs at the level of mRNA
-results in mRNA being degraded no less/no translation occurring so no/reduced amount of protein expression

Question 2

Anti-sense RNA history

Answer 2

• 1963: synthetic (not natural) anti-sense RNA blocked protein translation in cell-free extracts

• 1981: Natural anti-sense transcription (NAT) RNA discovered in bacteria

• 1980’s and 1990’s: NAT RNA discovered in eukaryotes
• Cis – transcribed from opposite strands of protein coding genes • Trans – transcribed from somewhere else in the genome

Question 3

Anti sense RNA

Answer 3

• 15-20 base oligonucleotides complementary to the “sense” mRNA
• Inhibit protein translation by inducing degradation of mRNA

Question 4

Synthetic anti- sense RNA: Applications

Answer 4

• Research: Inhibit the expression of gene(s) of interest for loss of function experiments.

• Therapy: Target genes responsible for a disease phenotype. E.g. Inflammatory genes or genes linked to tumour formation/growth

Question 5

RNAi facts

Answer 5

-double stranded RNA is required
-Naturally occurring non-coding RNA transcripts fold to generate double stranded microRNA (miRNA) loop structures
-miRNA are processed to make double stranded short interfering RNA (siRNA)

Question 6

Mechanism of RNAi

Answer 6

-in the nucleus primary miRNA gets converted(Folds up) to precursor miRNA
-it then gets processed by dicer bound to trans activation response element rna-binding protein(TRBP) which in the cytoplasm gives mature miRNA which then binds to RNA induced silencing complex bound to Argonaute 2 and is carried by micro rna to complements mRNA repressing transcription

Question 7

RNA Induced Silencing Complex (RISC)

Answer 7

RISC is a multi-protein complex
The identity and function of RISC components is still being investigated RISC cuts target mRNA transcripts
RISC is guided by processed miRNA or siRNA
RISC is the final step of the RNAi pathway
Argonaute family proteins are key components of RISC

Question 8

Argonaute

Answer 8

Argonautes are a family of related proteins Argonautes are a family of endonuclease enzymes Argonautes cut mRNA transcripts
mRNA cleavage is guided by miRNA/siRNA
Complementary base pairing between processed miRNA/siRNA and mRNA guides

Question 9

Mechanism of RNAi

Answer 9

-double stranded rna gets processed by dicer
-one processed strand is loaded into the risk complex
-risk complex is guided to messenger RNA by base pairing
-Messanger RNA gets chopped up by endonucleases enzymes into tiny pieces which means it wont be able to get used for transition meaning no protein

Question 10

RNAi summary

Answer 10

• Efficient RNAi uses double stranded RNA (dsRNA) molecules
• siRNA – small interfering RNA can be used as a tool to silence gene expression
• miRNA – microRNA are encoded by the genome
• siRNA and miRNA inhibit target gene expression
• siRNA and miRNA are processed by an enzyme called Dicer
• Dicer processes the dsRNA into ~21nt single stranded RNA
• The RNA Induced Silencing Complex (RISC) cleaves the target mRNA

Question 11

Porphyria

Answer 11

• Inherited genetic disorders
• Disorders related to enzymes
• Build up of haem precursors causes acute and chronic symptoms
• Haemoglobin -> Blood Science!

Question 12

lncRNA

Answer 12

> 200nts
Long non-coding RNA
-Regulate diverse cell processes.
-Not as well conserved as protein coding genes.
-Cell type specific?

Question 13

snoRNA

Answer 13

-60-300nts
-Small nucleolar RNA
-Processing of ribosomal RNA

Question 14

snRNA

Answer 14

~150nts
Small nuclear RNA
Splicing?

Question 15

piRNA

Answer 15

26-31nts
Piwi interacting RNA
Interact with piwi proteins to maintain genomic stability of germ line cells.