The C-terminal domain of mRNA-decapping enzyme in Metazoa is responsible for trimerisation [1].

1: DCP1 forms asymmetric trimers to assemble into active mRNA decapping complexes in metazoa. Tritschler F, Braun JE, Motz C, Igreja C, Haas G, Truffault V, Izaurralde E, Weichenrieder O; Proc Natl Acad Sci U S A. 2009;106:21591-21596. PMID:19966221