The function of USP38 (ubiquitin specific peptidase 38, Ensembl gene identifier ENSG00000170185) is as follows. Deubiquitinating enzyme that plays a role in various cellular processes, including DNA repair, cell cycle regulation, and immune response (PubMed:22689415, PubMed:30497519, PubMed:31874856, PubMed:35238669). Plays a role in the inhibition of type I interferon signaling by mediating the 'Lys-33' to 'Lys-48' ubiquitination transition of TBK1 leading to its degradation (PubMed:27692986). Cleaves the ubiquitin chain from the histone demethylase LSD1/KDM1A and prevents it from degradation by the 26S proteasome, thus maintaining LSD1 protein level in cells (PubMed:30497519). Plays a role in the DNA damage response by regulating the deacetylase activity of HDAC1 (PubMed:31874856). Mechanistically, removes the 'Lys-63'-linked ubiquitin chain promoting the deacetylase activity of HDAC1 in response to DNA damage (PubMed:31874856). Also acts as a specific deubiquitinase of histone deacetylase 3/HDAC3 and cleaves its 'Lys-63'-linked ubiquitin chains to lower its histone deacetylase activity (PubMed:32404892). Regulates MYC levels and cell proliferation via antagonizing ubiquitin E3 ligase FBXW7 thereby preventing MYC 'Lys-48'- linked ubiquitination and degradation (PubMed:34102342). Participates in antiviral response by removing both 'Lys-48'-linked and 'Lys-63'- linked polyubiquitination of Zika virus envelope protein E (PubMed:34696459). Constitutively associated with IL-33R/IL1RL1, deconjugates its 'Lys-27'-linked polyubiquitination resulting in its autophagic degradation (PubMed:35238669). {ECO:0000269|PubMed:22689415, ECO:0000269|PubMed:27692986, ECO:0000269|PubMed:30497519, ECO:0000269|PubMed:31874856, ECO:0000269|PubMed:32404892, ECO:0000269|PubMed:34102342, ECO:0000269|PubMed:34696459, ECO:0000269|PubMed:35238669}.