Regulatory subunit of serine/threonine-protein phosphatase 4 (PP4). May regulate the activity of PPP4C at centrosomal microtubule organizing centers. Serine/threonine-protein phosphatase 4 (PP4) occurs in different assemblies of the catalytic and one or more regulatory subunits. Component of the PP4 complex PPP4C-PPP4R2-PPP4R3B. In interphase localized in the cytoplasm and (with higher levels) the nucleus. During metaphase located in pericentriolar regions. Moderately expressed in tissues and specific brain regions examined. May be due to intron retention. Belongs to the SMEK family.