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. {ECO:0000269|PubMed:10394921; ECO:0000269|PubMed:10523645; ECO:0000269|PubMed:10747033; ECO:0000269|PubMed:10761922; ECO:0000269|PubMed:10779343; ECO:0000269|PubMed:10913177; ECO:0000269|PubMed:11027264; ECO:0000269|PubMed:11514438; ECO:0000269|PubMed:12773554; ECO:0000269|PubMed:16179257; ECO:0000269|PubMed:17429074; ECO:0000269|PubMed:17513695; ECO:0000269|PubMed:17875743; ECO:0000269|PubMed:18086885; ECO:0000269|PubMed:19901074; ECO:0000269|PubMed:20832728; ECO:0000269|PubMed:24247251; ECO:0000269|PubMed:8816497; ECO:0000269|PubMed:8972867}.