A) RECC contains 12 common proteins, of which three (KREX2, KREPA2, and KREL1) comprise a deletion subcomplex and three (KRET2, KREPA1, and KREL2) comprise an insertion subcomplex. OB-fold containing proteins KREPA3, KREPA6, KREPA4, and KREPA5 maintain protein-protein interactions. Zinc-finger containing KREPB4 and KREPB5 are thought to interact with endonucleases KREN1, KREN2, and KREN3 and their respective partners KREPB8, KREPB7, and KREPB6. KRENs interact with the insertion subcomplex and their KRPEB partners interact with the deletion subcomplex. B) There are three distinct classes of RECC, which differ in the associated KREN endonuclease and KREP partner proteins. KREN1/KREPB6 also associate with exoribonuclease KREX1. KREN1 containing RECCs catalyze U deletion, KREN2 containing RECCs catalyze U insertion, and KREN3 containing RECCs catalyze insertion specifically into cox2 mRNA.