Authors

Discussion

5' to 3' decay is the major mRNA degradation pathway in many organisms, including trypanosomes. First, the m⁷G cap is removed by the nudix domain hydrolase Dcp2, which is part of a larger decapping complex. Trypanosomes lack homologues to all decapping complex proteins and we have recently identified an ApaH-like phosphatase (TbALPH1) as the major mRNA decapping enzyme of trypanosomes. In vitro, TbALPH1 has mRNA decapping activity in a wide range of conditions without cap-type preference and surprisingly, largely independent on its C and N terminal domains that embed the catalytic domain. In vivo, these C- and N-terminal extensions determine enzyme localisation and protein interactions, likely regulating enzyme specificity. Even though ApaH-like phosphatases are present in all eukaryotic super-groups, our phylogenetic studies strongly suggest that their usage in mRNA decapping is unique to kinetoplastida.