Component of the decapping complex necessary for the degradation of mRNAs, both in normal mRNA turnover and in nonsense-mediated mRNA decay. Removes the 7-methyl guanine cap structure from mRNA molecules, yielding a 5'-phosphorylated mRNA fragment and 7m-GDP. Decapping is the major pathway of mRNA degradation in yeast. It occurs through deadenylation, decapping and subsequent 5' to 3' exonucleolytic decay of the transcript body. DCP1 is activated by the DEAD-box helicase DHH1 and destabilizes the eIF-4F cap-binding complex from the mRNA. Component of the decapping complex composed of DCP1 and DCP2. Interacts with mRNAs, DHH1, LSM1, LSM2, LSM3, LSM4, LSM5, LSM6, LSM7, and the cap-binding proteins PAB1 and TIF4632/eIF-4G. Is concentrated in several cytoplasmic foci called P bodies (or cytoplasmic processing bodies) which represent sites of mRNA decapping and 5' to 3' exonucleotidic decay. Phosphorylated. Present with 2880 molecules/cell in log phase SD medium. Belongs to the DCP1 family.