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What is RNA editing?
The changing of an RNA sequence from it's transcribed sequence to something else.
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What Organelle RNAs demonstrate editing?
- Nuclear RNAs
- Mitochondrial RNAs
- Chloroplast RNAs
- Viral RNA
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What Nuclear RNAs are editing?
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What Mitochondrial RNAs are edited?
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What Chloroplast RNAs are edited?
mRNA
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What specific Virus demonstrates RNA editing?
Hepatitis Delta Virus.
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What are some examples of RNA editing?
- A-to-I Conversion.
- C-to-U Conversion.
- U Instertion/Deletion
- Insertion of C Residues.
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What is another name for C-to-U conversion?
Deamination
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What does Deamination refer to?
C-to-U conversion.
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In conversion of A-to-I, what is the I read as?
Guanine (G).
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Does RNA editing occur in Prokaryotes?
No, none has been observed.
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If a given amino acid sequence is,
Lys-Gly-Pro-Leu
Is it always possible to determine the initial DNA sequence?
No, because RNA editing sometimes changes the transcript.
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Eubacteria and Archaea are examples of?
Prokaryotes.
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Where does insetion of U residues occur? (What organelle).
In the Mitochondria of Trypanosomes.
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What is a Trypanosome?
A single celled Parasitic Protozoan.
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Where does insertion of C Residues occur? (What Organelle)
Slime Mold Mitochondria.
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What RNAs tend to be affected by C Insertion?
rRNA, tRNA and mRNA
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In Mammals, where does C-to-U converstion occur?
In the intestine (Affects Apoprotein B mRNA).
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In Plants where does C-to-U conversion occur?
In Mitochondria and Chloroplasts.
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Where does A-to-I editing tend to occur in mammals?
- In the nucleus.
- Affects Glutamate and Serotonin 2c Receptors.
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What specific edit does Hepatitis Delta Virus demonstrate?
A-to-I conversion.
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How was U-Insertion first discovered?
Researcher noticed an mRNA product did not match it's "parent" DNA.
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What was the observation in Trypanosome RNA that lead to U-Insertion discovery?
A -1 Frameshift at the C-Terminus, Caused by addition of four U's.
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What protein was used to first identify U-Insertion?
Trypanosome Cox2p.
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How is it determined where U insertion/Deletion should occur?
- Guide RNAs will base pair to the site.
- Often, editing creates sites for further modification.
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How is the exact site of U insertion/deletion defined?
Bulges at the site (Not all Base Pairings are canonical).
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What is the role of anchor sequences in RNA editing?
Sites of binding for the guide RNA. They do not take part in the actual editing but serve help complimentarity.
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One U is always modified for each editing event. True or False?
False. Multiple U's can be edited in each event.
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What enzyme is responsible for A-to-I editing?
Adenosine Deaminase acting on RNA (ADAR).
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What are the ADARs found in humans?
ADAR 1, ADAR 2 and ADAR 3.
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Which human ADAR is found in the brain?
ADAR 3
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What type of molecules does Adenosine Deaminase acting on RNA target?
Double Stranded RNA.
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What are two key roles of ADARs?
- Defense (Interfering with foreign RNA).
- Control of splicing.
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How does and ADAR act as a defense system?
Through non-specific editing.
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How does an ADAR act to control splicing?
Through Specific Editing.
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What are some examples of ADARs that undergo Deamination?
- Glutamate Subunit Receptor B.
- Serotonin Receptor 5-HT2c.
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How does A-to-I editing affect the Glutamate receptor?
Changes the Glutamine (CAG) to an Argenine (CIG "CGG").
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How does A-to-I editing affect the Serotonin Recpetor 5-HT2c?
- It can change 3 amines in the GCPR's cytoplasmic loop.
- Lle (AUA) -> Met (AUI) -> Val (IUA/IUI)
- Asn (AAU) ->Asp (IAU)/Ser (AIU) -> Gly (IIU)
- Lle (AUU) -> Val (IUU)
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Where is Apo-B found?
In the Liver.
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How is the Apo-B48 protein produced from Apo-B mRNA?
- The CAA undergoes C-to-U editing becoming UAA (A transaltional STOP codon).
- The resulting protein is the stunted N-Terminus.
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HOw is the Apo-B100 protein formed?
- The mRNA is transcribed without any unique editing.
- The protein has two domains (N and C Termini).
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What are the two domains in the Apo-B100 protein?
- The N-Terminus (Lipid Association)
- The C-Terminus (Binds to Membrane LDL receptors).
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