MKI67 FHA Domain Interacting Nucleolar Phosphoprotein (MKI67IP)

NIFK amino acids 226 to 269 interacted with the MKI67 FHA domain and that the thr234 and thr238 residues were required for NIFK-MKI67 binding in a mitosis-specific and phosphorylation-dependent manner.The deduced 293-amino acid protein has a calculated molecular mass of 34 kD and contains a potential RNA-binding domain. NIFK shares 54% and 75% amino acid identity to its mouse homolog overall and over the RNA-binding domain, respectively. Immunocytochemical studies localized NIFK primarily to the nucleoli with much reduced staining observed after RNAse treatment of cells, suggesting that NIFK is an RNA-binding protein. After RNAse treatment, the remaining NIFK protein was detected at the outer region of nucleoli and may colocalize with MKI67 at the surface of mitotic chromosomes.