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Abstract
Centromeres, defined by CENP-A-containing nucleosomes, direct the assembly of kinetochores for spindle attachment. In mitosis, CENP-A and the constitutive centromere-associated network (CCAN) of the inner kinetochore are arranged into bipartite subdomains within clearings of chromatin. However, it remains unclear whether any of these features exist before mitosis. We show that in interphase, CENP-A and the CCAN assemble \~200-300 nm shell-like structures that enclose a chromatin-poor central cavity. Strikingly, this cavity is occupied by the interphase-specific CENP-A chaperone complex, which promotes CENP-A assembly once per cell cycle. However, chaperone presence, but not CENP-A incorporation, is required to generate both the shell architecture and the chromatin clearing. The CCAN scaffold CENP-C, which links CENP-A nucleosomes to the chaperone complex, exhibits radial organization spanning the entire structure and is essential for its formation. These data uncover a previously unrecognized structural role for the CENP-A chaperone machinery in establishing interphase centromere architecture and suggest a mechanism by which this machinery configures centromeres for faithful kinetochore assembly and genome stability.
