Pre-60S-associated cytoplasmic factor involved in the cytoplasmic maturation of the 60S subunit. Homo- and heterodimer. Associates with pre-60S ribosomal particles. Interacts with MELK and MYBL2. Interacts with DNAJC21. Phosphorylated by MELK. The phosphorylation may redirect the protein to the nucleus. Ubiquitinated by HECTD1, leading to its degradation. Belongs to the REI1 family.