A transcript of maxicircle or minicircle DNA, that in lower eukaryotes is thought to function in RNA editing, i.e. by the addition or deletion of U residues at specific sites in the coding regions of mRNA, itself derived from maxicircle DNA as an untranslatable cryptogene, the creation of a translatable open reading frame. The gRNA attaches to an unedited region (pre-edited region, PER) which at a GA-rich sequence anchors the oligo-U 3'-end of the gRNA and at a downstream sequence anchors the complementary 5'-end of the gRNA. Between the two anchored regions of the gRNA, a non-complementary oligonucleotide sequence loops out. An endonuclease cleaves the PER between the two anchors and uses a G residue of the gRNA loop as a template to patch in a U residue. The gRNA is then free to migrate to another site for editing. In some cases this mechanism inserts nearly half the U residues necessary for translation of a mRNA. This extensive editing of a single mRNA is termed pan-edition.