Component of the BRISC complex that specifically cleaves 'Lys-63'-linked polyubiquitin, leaving the last ubiquitin chain attached to its substrates (PubMed:26344097). Does not have activity by itself, but the catalytic subunit BRCC3/BRCC36 needs to be associated into a heterotetramer with FAM175B for minimal in vitro activity (PubMed:26344097). May act as a central scaffold protein that assembles the various components of the BRISC complex and retains them in the cytoplasm (By similarity). 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 numa1 (By similarity). Component of the BRISC complex, at least composed of FAM175B/ABRO1, BRCC3/BRCC36, BABAM2 and BABAM1/NBA1. Within the complex, interacts directly with BRCC3/BRCC36. The heterodimer with BRCC3/BRCC36 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 FAM175 family. Abro1 subfamily. Expected to lack catalytic activity.