The p150N domain of Chromatin Assembly Factor-1 regulates Ki-67 accumulation on the mitotic perichromosomal layer

Chromatin Assembly Factor 1 (CAF-1) deposits histones during DNA synthesis. The p150 subunit of human CAF-1 contains an N-terminal domain (p150N) that is dispensable for histone deposition but which promotes the localization of specific loci (Nucleolar-Associated Domains, or \"NADs\") and proteins to the nucleolus during interphase. One of the p150N-regulated proteins is proliferation antigen Ki-67, whose depletion also decreases the nucleolar association of NADs. Ki-67 is also a fundamental component of the perichromosomal layer (PCL), a sheath of proteins surrounding condensed chromosomes during mitosis. We show here that a subset of p150 localizes to the PCL during mitosis, and that p150N is required for normal levels of Ki-67 accumulation on the PCL. This activity requires the Sumoylation Interacting Motif (SIM) within p150N, which is also required for the nucleolar localization of NADs and Ki-67 during interphase. In this manner, p150N coordinates both interphase and mitotic nuclear structures via Ki67.