Motifs in the amino-terminus of CENP-A are required for its accumulation within the nucleus and at the centromere

Centromere protein A (CENP-A) is a variant of core histone H3 that marks the centromere's location on the chromosome. The mechanisms that target the protein to the nucleus and the centromere have not been defined. In this study, we found that deletion of the first 53 but not the first 29 residues of CENP-A from the amino-terminus, resulted in its cytoplasmic localization. Two motifs, R(42)R(43)R(44) and K(49)R(52)K(53)K(56), which are reported to be required for DNA contact in the centromere nucleosome, were found to be critical for CENP-A nuclear accumulation. These two motifs potentially mediated its interaction with Importin-β but were not involved in CENP-A centromeric localization. A third novel motif, L(60)L(61)I(62)R(63)K(64), was found to be essential for the centromeric accumulation of CENP-A. The nonpolar hydrophobic residues L(60)L(61)I(62), but not the basic residues R(63)K(64), were found to be the most important residues. A protein interaction assay suggested that this motif is not involved in the interaction of CENP-A with its deposition factors but potentially mediates its interaction with core histone H4 and CENP-B. Our study uncovered the role of the amino-terminus of CENP-A in localization.