RNA EDITING

Question 1

What is RNA editing?

Answer 1

One of the three steps of RNA maturation:
1. RNA processing
2. RNA modification
3. RNA editing

Question 2

Name the two main types of RNA editing

Answer 2

Substitution Editing: One nucleotide is replaced by another. Takes place in both coding and non-coding regions.
Insertion/ deletion editing (indel): length of the RNA molecule changes, introns (non-coding regions)

Question 3

Which factors are required for the RNA-editing mechanism, that deletes uridines into mRNAs of trypanosomes?

Answer 3

1. Guide RNA
2. Proteins
3. Endonuclease
4. ExoUase: U-specific 3’ exonuclease
5. RNA ligase

Question 3

Which factors are required for the RNA-editing mechanism, that inserts uridines into mRNAs of trypanosomes?

Answer 3

1. Guide RNA
2. Proteins
3. Endonuclease
4. TUTase (terminal uridyl transferase)
5. RNA ligase

Question 4

Which protein family is involved in RNA editing in organelles?
Explain the name of this protein family.
What other functions besides RNA editing do they have?

Answer 4

PPR: Pentatrico peptide repeats

It is called so because these proteins contain peptides and are made up of 35 amino acids that are repeated approximately 30 times.

Other functions:

• involved in RNA modification, splicing and stabilisation.
• involved in translation
• involved in regulation of organellar gene expression in Arabidobsis thalliana
• ## recognises RNA sequences so involved in RNA binding

Question 5

How does RNA editing in plant organelles change the mRNA and the encoded protein?

Answer 5

On mRNA:

1. cytidine get converted to uridine
2. this may cause one codon specifying a single amino acid to change into another codon coding for a different AA
3. creation of start codon (AUG) or stop codon (UAA, UAG and UGA)

On encoded protein:

1. Amino acids change
2. Protein structure and function change
3. Protein domains get inserted or deleted
4. protein localization to specific subcellular compartments will get affected