CENP-I directly targets centromeric DNA to support CENP-A deposition and centromere maintenance

Abstract

The enrichment of histone H3 variant CENP-A is the epigenetic mark of centromere and initiates the assembly of the kinetochore at centromere. The kinetochore is a multi-subunit complex that ensures accurate attachment of microtubule centromere and faithful segregation of sister chromatids during mitosis. As a subunit of kinetochore, CENP-I localization at centromere also depends on CENP-A. However, whether and how CENP-I regulates CENP-A deposition and centromere identity remains unclear. Here, we identified that CENP-I directly interacts with the centromeric DNA and preferentially recognizes AT-rich elements of DNA via a consecutive DNA-binding surface formed by conserved charged residues at the end of N-terminal HEAT repeats. The DNA binding–deficient mutants of CENP-I retained the interaction with CENP-H/K and CENP-M, but significantly diminished the centromeric localization of CENP-I and chromosome alignment in mitosis. Moreover, the DNA binding of CENP-I is required for the centromeric loading of newly synthesized CENP-A. CENP-I stabilizes CENP-A nucleosomes upon binding to nucleosomal DNA instead of histones. These findings unveiled the molecular mechanism of how CENP-I promotes and stabilizes CENP-A deposition and would be insightful for understanding the dynamic interplay of centromere and kinetochore during cell cycle.