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Molecular Cloning and Sequence Analysis of Hamster CENP-A cDNA

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Molecular Cloning and Sequence Analysis of Hamster CENP-A cDNA

Javier Figueroa et al. BMC Genomics.

Abstract

Background: 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.

Results: 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 autoimmune diseases is not conserved in the hamster protein.

Conclusions: 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.

Figures

Figure 1
Figure 1
Nucleotide sequence of hamster CENP-A cDNA. Deduced amino acids of 129 encoded codons are shown in black. Numbers in the right indicate nucleotide position. The asterisk designates the stop codon. Two consensus polyadenylation signal sequences are shown in black underlined.
Figure 2
Figure 2
Alignment of hamster, mouse and human CENP-A amino acid sequences. The alignment has been shaded with identical residues. The C-terminal histone H3 fold domain (aa 37–129) is highly conserved. In contrast, several residues of the N-terminal tail are variable among the three species compared, including several deletions as shown. The accession numbers are as follows: hamster AJ428867 (this work); mouse AF012708-10 and human U14518-19.

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