The function of MYSM1 (Myb like, SWIRM and MPN domains 1, Ensembl gene identifier ENSG00000162601) is as follows. Metalloprotease with deubiquitinase activity that plays important regulator roles in hematopoietic stem cell function, blood cell production and immune response (PubMed:24062447, PubMed:26220525, PubMed:28115216). Participates in the normal programming of B-cell responses to antigen after the maturation process (By similarity). Within the cytoplasm, plays critical roles in the repression of innate immunity and autoimmunity (PubMed:33086059). Removes 'Lys-63'-linked polyubiquitins from TRAF3 and TRAF6 complexes (By similarity). Attenuates NOD2-mediated inflammation and tissue injury by promoting 'Lys-63'-linked deubiquitination of RIPK2 component (By similarity). Suppresses the CGAS-STING1 signaling pathway by cleaving STING1 'Lys- 63'-linked ubiquitin chains (PubMed:33086059). In the nucleus, acts as a hematopoietic transcription regulator derepressing a range of genes essential for normal stem cell differentiation including EBF1 and PAX5 in B-cells, ID2 in NK-cell progenitor or FLT3 in dendritic cell precursors (PubMed:24062447). Deubiquitinates monoubiquitinated histone H2A, a specific tag for epigenetic transcriptional repression, leading to dissociation of histone H1 from the nucleosome (PubMed:17707232). {ECO:0000250|UniProtKB:Q69Z66, ECO:0000269|PubMed:17707232, ECO:0000269|PubMed:22169041, ECO:0000269|PubMed:24062447, ECO:0000269|PubMed:26220525, ECO:0000269|PubMed:28115216, ECO:0000269|PubMed:33086059}.