SECTION G – RNA SYNTHESIS AND PROCESSING G7  Processing of eukaryotic  pre-mRNA

RNA editing RNA editing can change the sequence of an mRNA molecule after synthesis and processing; nucleotides may be substituted, added or deleted. In human liver, apolipoprotein B pre-mRNA does not undergo editing and translation yields apolipoprotein B100. In the small intestine, RNA editing converts a single C residue in apolipoprotein B pre-mRNA to U, changing a codon for glutamine (CAA) to a termination codon (UAA). Translation of the edited mRNA yields the shorter protein, apolipoprotein B48, that lacks a protein domain for receptor binding. Many other examples of editing occur, including trypanosome mitochondrial mRNAs, where over half of the uridines in the final mRNA are acquired through the editing process.