RNA modifications - lecture 17 Flashcards
What molecule was used to learn about RNA modifications?
tRNA
What are wobble - position modifications?
34 , first position of the anticodon. the wobble position means it can bind to different sequences on the code. E.g G can interact with C and U
What is a common mitochondrial mutation in methionine tRNA?
5 - formylcytosine
What enzyme is needed to convert methionine rTNA in to 5 methyl cytosine?
NSUN3
What enzyme is needed to convert 5 methyl cytosine to 5 formylcytosine?
ABH1
What is he most common mutation in mammalian mRNA?
N6 - methyl adenosine (m6A)
How is the M6A mutation mapped?
- fragment the mRNA
- Use and antibody thats been raised to the modification
- Wash away any antibody thats unbound , isolate the modifications
- Know which fragments have the M6A modification , can sequence these fragments
What do the proteins YTHDF1 and YTHDF2 bind to?
M6A modification
What does YTHDF1 do?
regulates its translation , speeds it up
What does YTHDF2 do?
Results in a decay of the mRNA
What is a less common modification in mRNA?
5 - methyl cytosine
What are older ways to detect 5mC in mRNA?
- bisulphite sequencing ( not very good get a lot of false positives)
- Raise an antibody to the modification
What are newer ways to detect 5mC in mRNA?
- express the enzyme which catalyses the modification , this forms a covalent bond
- Freeze that complex, map where the covalent bond has formed
Where does the methylation of cytosine most commonly occur? what sequence
CTCCA , Methylation on the first C.
Methylation found in 3 prime UTR too most commonly
How do you form inosine bases?
Enzymatic modification of adenosine bases
What is special about the inosine modification/?
- Results in an edit in the coding sequence
- Has the capability to change amino acids
What enzymes convert Adenosine to Inosine?
ADAR1 and ADAR2
What are Inosines read as by the cell
G
Where is the AMPA receptor found?
major receptor in the Brain
What happens when the mRNA of the AMPMA receptor is edited?
Converts Glutamine into Arginine.
This means that the channel is closed
