Recruits the serine/threonine-protein phosphatase PPP1CA to prevents excessive phosphorylation of the translation initiation factor eIF-2A/EIF2S1, thereby reversing the shut-off of protein synthesis initiated by stress-inducible kinases and facilitating recovery of cells from stress (PubMed:26095357, PubMed:26742780). Down-regulates the TGF-beta signaling pathway by promoting dephosphorylation of TGFB1 by PP1 (PubMed:14718519). May promote apoptosis by inducing p53/TP53 phosphorylation on 'Ser-15' (PubMed:14635196). Plays an essential role in autophagy by tuning translation during starvation, thus enabling lysosomal biogenesis and a sustained autophagic flux (PubMed:32978159). Also acts a viral restriction factor by attenuating HIV-1 replication (PubMed:31778897). Mechanistically, mediates the inhibition of HIV-1 TAR RNA-mediated translation (PubMed:31778897). {ECO:0000269|PubMed:11564868, ECO:0000269|PubMed:12556489, ECO:0000269|PubMed:14635196, ECO:0000269|PubMed:14718519, ECO:0000269|PubMed:26095357, ECO:0000269|PubMed:31778897, ECO:0000269|PubMed:8139541}. (Microbial infection) Promotes enterovirus 71 replication by mediating the internal ribosome entry site (IRES) activity of viral 5'- UTR. . This is the function of Ensembl gene identifier ENSG00000087074 (PPP1R15A, protein phosphatase 1 regulatory subunit 15A).