Interactions with multiple inner kinetochore proteins determine mitotic localization of FACT

The FAcilitates Chromatin Transcription (FACT) complex is a dimeric histone chaperone that operates on chromatin during transcription and replication. FACT also interacts with a specialized centromeric nucleosome containing the histone H3 variant centromere protein A (CENP-A) and with CENP-TW, two subunits of the constitutive centromere-associated network (CCAN), a 16-protein complex associated with CENP-A. The significance of these interactions remains elusive. Here, we show that FACT has multiple additional binding sites on CCAN. The interaction with CCAN is strongly stimulated by casein kinase II phosphorylation of FACT. Mitotic localization of FACT to kinetochores is strictly dependent on specific CCAN subcomplexes. Conversely, CENP-TW requires FACT for stable localization. Unexpectedly, we also find that DNA readily displaces FACT from CCAN, supporting the speculation that FACT becomes recruited through a pool of CCAN that is not stably integrated into chromatin. Collectively, our results point to a potential role of FACT in chaperoning CCAN during transcription or in the stabilization of CCAN at the centromere during the cell cycle.