L4 - Post-transcriptional gene regulation – RNA interference (RNAi), siRNA & miRNA Flashcards
Define RNAi
RNAi = RNA interference: The process of enabling a cell to prevent the expression of/’silence’ a gene
Define dsRNA
Double-stranded RNA
Define siRNA
Small interfering RNA
Define miRNA
Micro interfering RNA
Define RISC
RNA-induced silencing complex
Define RDR’s
RNA-dependant RNA Polymerases
Describe differences between siRNA’s & miRNA’s
siRNA’s = Longer than miRNA’s, therefore are more specific in their mRNA binding, as due to their increased length, they can only bind to specific mRNA’s
siRNA’s & miRNA’s are naturally occurring types of _____ found in eukaryotes and some prokaryotes.
siRNA’s & miRNA’s are naturally occurring types of dsRNA found in eukaryotes and some prokaryotes.
What do siRNA’s & miRNA’s do?
They bind to mRNA and cut it, reducing protein transcription
What enzyme catalyses the production of dsRNA?
RNA-dependant RNA Polymerases (RDR’s)
What enzyme cuts long dsRNA into siRNA?
Dicer
dsRNA (either siRNA or miRNA) binds to a protein that splits the strands and keeps one strand bound to it.
What is the name of this protein?
The ‘Argonaute’ protein
When the Argonaute protein only has one of the strands of the mRNA, it is called an…
RNA-induced silencing complex (RISC)
State the 6 steps to how siRNA’s & miRNA’s work
1) RNA-dependant RNA Polymerases (RDR’s) catalyse the production of dsRNA
2) An enzyme called dicer cuts long dsRNA into siRNA
3) The dsRNA (either siRNA or miRNA) binds to a protein (called the Argonaute protein) which splits the strands and keeps one strand bound to it
4) This protein now only has one of the strands of the mRNA. (It has now become what is known as an RNA-induced silencing complex (RISC)).
5) The protein with the dsRNA then binds with the mRNA by complementary base pairing
6) Either the mRNA is hydrolysed via RNA hydrolase OR ribosomes are prevented from attaching to the mRNA. Either way, this leads to the mRNA not being able to be transcribed.
