Describe the role of two forms of RNA editing that lead to changes in the size and sequence of pre-mRNAs. Briefly describe several examples of each form of editing, including their impact on respective protein products.

Key Concepts

RNA Editing

RNA editing is a molecular process that alters the nucleotide sequence of RNA transcripts after they have been synthesized from DNA. This modification can lead to changes in the resulting protein products by either changing the amino acid sequence or affecting the stability and localization of the mRNA. Two primary forms of RNA editing are A-to-I editing and C-to-U editing, which can significantly influence gene expression and protein function.

A-to-I Editing

A-to-I editing involves the conversion of adenosine (A) to inosine (I) in RNA molecules, primarily mediated by the enzyme ADAR (adenosine deaminases acting on RNA). This type of editing can alter codons, potentially changing the amino acid sequence of proteins or creating new splice sites. For example, in the glutamate receptor gene, A-to-I editing can affect receptor function and neuronal signaling, impacting synaptic plasticity.

C-to-U Editing

C-to-U editing refers to the deamination of cytidine (C) to uridine (U) in RNA, primarily catalyzed by the enzyme APOBEC. This form of editing can lead to changes in the coding sequence of mRNAs, affecting protein structure and function. An example is the editing of the apolipoprotein B (APOB) mRNA, which results in the production of two different protein isoforms, influencing lipid metabolism and cardiovascular health.