The function of DUSP26 (dual specificity phosphatase 26, Ensembl gene identifier ENSG00000133878) is as follows. Inactivates MAPK1 and MAPK3 which leads to dephosphorylation of heat shock factor protein 4 and a reduction in its DNA-binding activity. Inhibits MAP kinase p38 by dephosphorylating it and inhibits p38-mediated apoptosis in anaplastic thyroid cancer cells. Can also induce activation of MAP kinase p38 and c-Jun N-terminal kinase (JNK). {ECO:0000269|PubMed:15796912, ECO:0000269|PubMed:16581800, ECO:0000269|PubMed:16924234, ECO:0000269|PubMed:17001450}.