#RNA editing

Processing of mRNA, rRNA, tRNA

Guide RNAs are required for RNA editing in

In mitochondria of trypanosomatids including Trypanosoma brucei, many protein-coding genes exist as cryptogenes requiring extensive uridine insertion and deletion editing guided by small noncoding guide RNAs encoded in kinetoplast DNA. Guide RNAs form short anchor duplex with pre-messenger RNA upstream of editing sites, specifying positions via base pairing where editosome complex containing endonuclease, 3' terminal uridylyltransferase TUTase adding uridines, and RNA ligase executes insertions. Editing can add hundreds of uridines and delete dozens, dramatically remodeling open reading frames

Ref: Berg et al., Biochemistry, 9th ed., Chapter 28: Guide RNAs required for editing mitochondria of trypanosomes; Cell, Trypanosome editosome structure

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Processing of mRNA, rRNA, tRNA

A to I RNA editing is catalyzed by

Adenosine to inosine editing, most frequent editing in mammalian transcriptomes, catalyzed by ADAR family adenosine deaminases acting on RNA containing double-stranded regions. Enzymes ADAR1 p110 p150 and ADAR2 deaminate adenosine at C6 position via hydrolytic deamination producing inosine, which ribosome and spliceosome read as guanosine due to base pairing with cytidine. Targets include glutamate receptor GluA2 Q/R site altering calcium permeability, serotonin 5HT2C receptor fine-tuning signaling. ADARs contain dsRNA binding domains, deaminase domain, editing complementary sequences often wi

Ref: Lodish et al., Molecular Cell Biology, 9th ed., Chapter 11: ADAR catalyzes A-to-I editing; Nature Rev Mol Cell Biol, ADAR editing functions

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Processing of mRNA, rRNA, tRNA

C to U RNA editing occurs in

Classic example of mammalian C-to-U editing occurs in apolipoprotein B messenger RNA in small intestine, converting glutamine codon CAA at codon two thousand one hundred fifty-three to stop codon UAA, yielding truncated ApoB48 protein of two thousand one hundred fifty-two amino acids versus full-length ApoB100 of four thousand five hundred thirty-six amino acids synthesized in liver. ApoB48 lacks low-density lipoprotein receptor binding domain, essential for chylomicron formation. Editing mediated by APOBEC1 cytidine deaminase and ACF cofactor recognizing mooring sequence eleven nucleotides do

Ref: Lodish et al., Molecular Cell Biology, 9th ed., Chapter 11: C-to-U editing apolipoprotein B mRNA; Berg et al., Biochemistry, APOBEC1 mechanism

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Processing of mRNA, rRNA, tRNA

RNA editing involves

RNA editing encompasses post-transcriptional processes altering nucleotide sequence of primary transcript after synthesis, thereby changing coding potential without modifying genome. Mechanisms include site-specific insertion or deletion of nucleotides, such as uridine insertion guided by guide RNAs in trypanosome mitochondria creating correct reading frames, and deaminase-mediated base conversions C-to-U in apolipoprotein B mRNA or A-to-I in neuronal receptors catalyzed by ADAR enzymes converting codon and affecting splicing patterns. Editing can affect stability, localization, and translatio

Ref: Berg et al., Biochemistry, 9th ed., Chapter 28: RNA editing involves addition/deletion of nucleotides; Lodish 9th ed., Overview of editing types

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