A-to-I mRNA Editing in Animals

A-to-I mRNA Editing in Animals Latest News

Researchers from China recently reported that it’s hard to make sense of the widespread persistence of A-to-I mRNA editing in animals.

Concept and Mechanism

• DNA acts like a recipe book for building proteins using 20 amino acids. Each recipe (i.e., gene) is transcribed into messenger RNA (mRNA).
• The mRNA is then read by ribosomes to assemble proteins. The mRNA is composed of four nucleotide bases: A (adenosine), U, G, and C.
• In A-to-I mRNA editing, the adenosine (A) in mRNA is enzymatically converted into inosine (I) by proteins called ADARs (Adenosine Deaminase Acting on RNA).
• The ribosome reads inosine as guanine (G), altering the protein’s amino acid sequence post-transcriptionally, without any change in the DNA.
• Functional Impact: A-to-I editing can change the codon identity, thereby producing a different amino acid in the resulting protein.
  • This may lead to functional protein diversification and alteration in protein stability or activity.
• A major risk is misreading stop codons:
  • A stop codon like UAG or UGA may be edited to UGG, coding for tryptophan.
  • This allows the ribosome to continue protein synthesis, potentially creating abnormally long or malfunctioning proteins.

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Discovery of PSC Genes

• Researchers identified 71 genes in F. graminearum that contain premature stop codons (UAG) in their unedited mRNA.
• These were termed PSC (premature stop codon-containing) genes.
• Deleting these genes had:
  • No impact during asexual growth.
  • But significant disruption during sexual development, proving the essentiality of A-to-I editing in these stages.

A-to-I mRNA Editing in Animals FAQs

Q1: What is A-to-I mRNA editing?
Ans: A-to-I mRNA editing is a post-transcriptional RNA modification where adenosine (A) is converted to inosine (I) by the ADAR (Adenosine Deaminase Acting on RNA) enzyme.

Q2: What is the significance of inosine in mRNA?
Ans: Inosine is read as guanosine (G) by the cellular machinery, which can alter the resulting protein sequence, potentially affecting its function.

Source: TH