Evolutionary origins of apoB mRNA editing: catalysis by a cytidine deaminase that has acquired a novel RNA-binding motif at its active site

Article Abstract:

The p27 enzyme involved in C to U editing of apoliprotein B100 mRNA has been found to be a zinc-containing cytidine residue deaminase, and its interaction with polymeric apoB mRNA substrate is essential for editing. The binding of p27 to mRNA is through amino acid residues used for zinc binding, proton shuttling and forming the alpha-beta-alpha structure present in the active site. The binding of this enzyme does not require the presence of a catalytically active site since mutation in the active site fails to prevent its binding to RNA. The enzyme may have evolved from enzymes that act on monomeric substrates through acquisition of polymeric substrate binding.

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A place in the world for RNA editing

Article Abstract:

In RNA editing, either cleavage or the addition or substitution of bases takes place. Conversion of a glutamine to stop codon (C to U) is seen in mammals and the mitochondria and chloroplasts of vascular plants and U to C editing is seen in pteridophyte mitochondria. RNA editing in the AMPA receptors changes their kinetic properties while the site editing involving the editing of the GluR-C pre-mRNA from a glutamine to a arginine codon decreases the calcium permeability of the AMPA channels. RNA editing in plants is probably unrelated to RNA editing in mammals.

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Direct visualization of uridylate deletion in vitro suggests a mechanism for kinetoplastid RNA editing

Article Abstract:

RNA editing is a form of RNA processing that involves the insertion and deletion of of uridylate residues within the coding regions of pre-mRNAs. This unusual form of RNA processing requires the action of guide RNAs that complement sequences to be edited. Visualization of uridylate deletion can be accomplished with the coincubation of a synthetic RNA and a radiolabeled substrate RNA in 20S fractions of T. brucei mitochondrial lysates. Research indicates that kinetoplastid RNA editing is characterized by nonproductive chimeric molecules end products.

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