The function of PPM1D (protein phosphatase, Mg2+/Mn2+ dependent 1D, Ensembl gene identifier ENSG00000170836) is as follows. Involved in the negative regulation of p53 expression (PubMed:23242139). Required for the relief of p53-dependent checkpoint mediated cell cycle arrest. Binds to and dephosphorylates 'Ser-15' of TP53 and 'Ser-345' of CHEK1 which contributes to the functional inactivation of these proteins (PubMed:15870257, PubMed:16311512). Mediates MAPK14 dephosphorylation and inactivation (PubMed:21283629). Is also an important regulator of global heterochromatin silencing and critical in maintaining genome integrity (By similarity). {ECO:0000250|UniProtKB:Q9QZ67, ECO:0000269|PubMed:15870257, ECO:0000269|PubMed:16311512, ECO:0000269|PubMed:21283629, ECO:0000269|PubMed:23242139}.