Metalloprotease that specifically cleaves 'Lys-63'-linked polyubiquitin chains, leaving the last ubiquitin chain attached to its substrates. Catalytic subunit of the BRISC complex; does not have activity by itself, but needs to be associated into a heterotetramer with ABRAXAS2 for minimal in vitro activity (PubMed:26344097). Plays a role in regulating the onset of apoptosis via its role in modulating 'Lys-63'-linked ubiquitination of target proteins (By similarity). Required for normal mitotic spindle assembly and microtubule attachment to kinetochores via its role in deubiquitinating spindle assembly factors (By similarity). Binds 1 zinc ion per subunit. Component of the BRISC complex, at least composed of ABRAXAS2, BRCC3/BRCC36, BABAM2 and BABAM1/NBA1. Within the complex, interacts directly with ABRAXAS2. The heterodimer with ABRAXAS2 assembles into a heterotetramer. The BRISC complex binds polyubiquitin. A minor proportion is detected in the nucleus. Translocates into the nucleus in response to DNA damage. Directly binds to microtubules and is detected at the minus end of K-fibers. Belongs to the peptidase M67A family. BRCC36 subfamily.