High Quality Content by WIKIPEDIA articles! The term RNA editing describes those molecular processes in which the information content in an RNA molecule is altered through a chemical change in the base makeup. To date, such changes have been observed in tRNA, rRNA, mRNA and microRNA molecules of eukaryotes but not prokaryotes. RNA editing occurs in the cell nucleus and cytosol, as well as in mitochondria and plastids, which are thought to have evolved from prokaryotic-like endosymbionts.