USP45 is a deubiquitylase, an enzyme that catalyses the removal of ubiquitin from target proteins. It binds ERCC1, the catalytic subunit of the XPF-ERCC1 DNA repair endonuclease, and deubiquitinates it. This promotes ERCC1 recruitment to sites of DNA damage and plays a role in the repair of UV-induced DNA damage. The deubiquitylase activity of USP45 is important for maintaining the DNA repair ability of XPF-ERCC1, a critical regulator of DNA repair processes. USP45 also catalyses the deubiquitination of SPDL1 and plays a role in cell migration.

The human USP45 gene encodes the protein Ubiquitin carboxyl-terminal hydrolase 45, which belongs to the peptidase C19 family and to the HGNC gene group of ubiquitin specific peptidases. UniProt records its subcellular locations as the photoreceptor inner segment, the cytoplasm and the nucleus. The mouse ortholog is Usp45, which is useful when planning work in rodent models.

Beyond DNA repair, USP45 may be involved in the maintenance of photoreceptor function and may play a role in normal retinal development. The gene was previously known by the alias MGC14793 and the name ubiquitin specific protease 45. Researchers studying genome stability, ubiquitin signalling or retinal biology can use the USP45 protein and gene as entry points into these processes, and USP45 antibody or USP45 ELISA kit reagents are common tools for examining its expression and function.