insert_CU true insert CU sequence An edit to insert a CU dinucleotide. SO:0000926 The type of RNA editing found in the mitochondria of Myxomycota, characterized by the insertion of mono- and dinucleotides in RNAs relative to their mtDNA template and in addition, C to U base conversion. The most common mononucleotide insertion is cytidine, although a number of uridine mononucleotides are inserted at specific sites. Adenine and guanine have not been observed in mononucleotide insertions. Five different dinucleotide insertions have been observed, GC, GU, CU, AU and AA. Both mono- and dinucleotide insertions create open reading frames in mRNA and contribute to highly conserved structural features of rRNAs and tRNAs.