Activator of decapping that functions as a general and active mechanism of translational repression and required for P-body formation. First decay factor recruited to mRNA, at a time when the mRNA is still associated with translation factors. Subsequently, PAT1 recruits the hepta-heterodimer LSM1-LSM7 complex to P-bodies. In association with the LSM1-LSM7 complex, stabilizes the 3' terminus of mRNAs. This association is also required for mosaic virus genomic RNA translation. Modulates the rates of mRNA-decapping that occur following deadenylation. Might be required for promoting the formation or the stabilization of the preinitiation translation complexes. Required for 40S ribosomal subunit joining to capped and/or polyadenylated mRNA. With other P-body components, enhances the formation of retrotransposition-competent Ty1 virus-like particles. Necessary for accurate chromosome transmission during cell division. Associates with the 40S ribosomal subunit. Associates with the heptameric LSM1-LSM7 complex. Interacts directly with LSM2 and LSM3 within the LSM1-LSM7 complex. Interacts with DHH1, LSM1, LSM5, RPB4, RPB7 and with topoisomerase TOP2. Interacts with CDC33, PAB1, TIF4631 and TIF4632 in an RNA-dependent manner. Binds mRNAs. The region at residues 254 to 422 is required for stimulation of decapping. The region at residues 422 to 763 is required for PAT1 and LSM1 to accumulate in P-bodies and responsible for translation repression and P-body assembly. Present with 656 molecules/cell in log phase SD medium. Belongs to the PAT1 family.