RNA editing

RNA editing modifies genetic information at the
RNA level. An important example is the apolipoprotein-
B gene involved in lipid metabolism. It
encodes a protein of 4538 amino acids, apolipoprotein
B. This is synthesized in the liver and
secreted into the blood, where it transports
lipids. A related shorter form of the protein with
2153 amino acids, Apo B-48 (250 kDa, instead of
512 kDa for Apo B-100), is synthesized in the intestine.
An intestinal deaminase converts a cytosine
in codon 2158, CAA (glutamine), to uracil
(UAA). This change results in a stop codon (UAA)
and thereby terminates translation at this site.