The centromere is a specialized locus that mediates chromosome movement during mitosis and meiosis. This chromosomal domain comprises a uniquely packaged form of heterochromatin that acts as a nucleus for the assembly of the kinetochore a trilaminar proteinaceous structure on the surface of each chromatid at the primary constriction. Kinetochores mediate interactions with the spindle fibers of the mitotic apparatus. Centromere protein A (CENP-A) is a histone H3-like protein specifically located to the inner plate of kinetochore at active centromeres. CENP-A works as a component of specialized nucleosomes at centromeres bound to arrays of repeat satellite DNA.
We have cloned the hamster homologue of human and mouse CENP-A. The cDNA isolated was found to contain an open reading frame encoding a polypeptide consisting of 129 amino acid residues with a C-terminal histone fold domain highly homologous to those of CENP-A and H3 sequences previously released. However, significant sequence divergence was found at the N-terminal region of hamster CENP-A that is five and eleven residues shorter than those of mouse and human respectively. Further, a human serine 7 residue, a target site for Aurora B kinase phosphorylation involved in the mechanism of cytokinesis, was not found in the hamster protein. A human autoepitope at the N-terminal region of CENP-A described in autoinmune diseases is not conserved in the hamster protein.
We have cloned the hamster cDNA for the centromeric protein CENP-A. Significant differences on protein sequence were found at the N-terminal tail of hamster CENP-A in comparison with that of human and mouse. Our results show a high degree of evolutionary divergence of kinetochore CENP-A proteins in mammals. This is related to the high diverse nucleotide repeat sequences found at the centromere DNA among species and support a current centromere model for kinetochore function and structural plasticity.