Decapping Reaction of mRNA Requires Dcp1 in Fission Yeast : Its Characterization in Different Species from Yeast to Human

Cleavage of the 5'-cap structure is involved in the major 5'-to-3' and nonsense-mediated mRNA decay pathways, and the protein complex consisting of Dcpl and Dcp2 has been identified as the species responsible for the decapping reaction in Saccharomyces cerevisiae and human. Although in vitro studies indicate that Dcp2 is catalytically an active component, the role of Dcp1 in the decapping reaction remains to be explored in organisms other than budding yeast. To elucidate the Dcp1-dependent decapping mechanisms, we identified the homologues of S. cerevisiae Dcpl (ScDcpl) in higher eukaryotes and analyzed their functions in the different species. The phenotypes of slow growth and mRNA stabilization induced by Scdcpl-gene disruption in budding yeast could be suppressed by the Shizosaccharomyces pombe SpDcpl but not by the human homologue hDcpl. In contrast, the same phenotypes caused by Spdcpl-gene disruption in fission yeast were effectively complemented by hDcpl and its partial sequence comparable to SpDcpl. These results indicate that not only Dcp2 but also Dcpl plays an indispensable role in mRNA-decay pathway and that the characteristics of Dcp1-dependent decapping reaction in fission yeast hold an intermediate position in the evolution of mRNA-decay machinery from budding yeast to mammals.