Centromere assembly requires the direct recognition of CENP-A nucleosomes by CENP-N

Abstract

Centromeres are specialized chromosomal domains that direct kinetochore assembly during mitosis. CENP-A, a histone H3-variant present exclusively in centromeric nucleosomes, is thought to act as an epigenetic mark that specifies centromere identity. Here we identify the essential centromere protein CENP-N as the first protein to selectively bind CENP-A nucleosomes but not H3 nucleosomes. CENP-N bound CENP-A nucleosomes in a DNA-sequence independent manner but did not bind soluble CENP-A/H4 tetramers. Mutations in CENP-N that reduced the affinity of CENP-N for CENP-A nucleosomes caused defects in CENP-N localization and had dominant effects on the recruitment of CENP-H, CENP-I and CENP-K to centromeres. Depletion of CENP-N with siRNA’s led to similar centromere assembly defects and resulted in reduced assembly of nascent CENP-A into centromeric chromatin. These data suggest that CENP-N interprets the information encoded within CENP-A nucleosomes and recruits to centromeric chromatin other proteins required for centromere function and propagation.