Lecture 14 - Regulation by microRNAs

Question 1

What are non-coding RNAs?

Answer 1

Non-coding RNAs = transcripts that do not code for a protein

• housekeeping ncRNAs (e.g rRNA, tRNA, snRNA)
• regulatory ncRNAs (controlling gene expression)
• ncRNAs of unknown function

Question 2

What are small non-coding RNAs?

Answer 2

1000s of sRNAs in higher eukaryotes

• Can influence gene expression at the transcriptional or post-transcriptional level (usually negatively)
• Act as sequence-specificity guides for effector complexes
• MicroRNAs (miRNAs) are a major class of small non-coding RNA

Question 3

How are small RNAs produced?

Answer 3

predominantly via the RNA interference pathway (RNAi) pathway
Pathway involves the ability of eukaryotes to recognise dsRNA and process it into small RNA segments, which in the early stages are still double-stranded. They then get unwound and form effect complexes - interaction between small RNA and protein.
RNA interference is also known as RNA silencing.
The sRNA + Argonaute effector complex can direct the sequence-specific cleavage of mRNAs with which the sRNA can pair.

Question 4

How can double stranded RNA be used in gene function analysis?

Answer 4

triggers targeted RNA degradation of complementary transcripts
Whatever dsRNA was introduced, as long as it was complementary to a gene of interest, they could switch off that gene - easy way to knock out gene, large potential for gene function analysis