Regulatory subunit of serine/threonine-protein phosphatase 4. The probable PP4 complex Pp4-19C-PPP4R2r-flfl (PPP4C-PPP4R2-PPP4R3) is required to prevent caspase induced cell death (in vitro). May be involved in DNA damage repair. Key mediator specific for the localization of mira and associated cell fate determinants during both interphase and mitosis. Nuclear Flfl is required to exclude mira/pros from the nucleus when inefficiently bound to the cytoskeleton/cortex, whereas cytosolic or membrane-associated flfl is required for the cortical association and asymmetric localization of mira/pros/brat/stau at metaphase and anaphase. Serine/threonine-protein phosphatase 4 (PP4) occurs in different assemblies of the catalytic and one or more regulatory subunits. Probably part of a PP4 PPP4C-PPP4R2-PPP4R3 complex containing Pp4-19C, PPP4R2r and flfl. Interacts with mira. Predominantly nuclear during interphase/prophase and cytoplasmic after nuclear envelope breakdown. Expressed in neuroblasts. Mutant larvae exhibit hypersensitivity to the anticancer drug cisplatin. Belongs to the SMEK family.