Adaptive evolution of centromere proteins in plants and animals
Paul B Talbert , Terri D Bryson and Steven Henikoff
Howard Hughes Medical Institute, Fred Hutchinson Cancer Research Center,
1100 Fairview Avenue N, Seattle, WA 98109-1024, USA

Journal of Biology 2004, 3:18     doi:10.1186/jbiol11

The electronic version of this article is the complete one and can be found
online at: http://jbiol.com/content/3/4/18

Received 25 May 2004
Revisions received 20 July 2004
Accepted 22 July 2004
Published 31 August 2004

© 2004 Talbert et al.; licensee BioMed Central Ltd.
This is an Open Access article distributed under the terms of the Creative
Commons Attribution License (http://creativecommons.org/licenses/by/2.0),
which permits unrestricted use, distribution, and reproduction in any
medium, provided the original work is properly cited.

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Abstract

Background
Centromeres represent the last frontiers of plant and animal genomics.
Although they perform a conserved function in chromosome segregation,
centromeres are typically composed of repetitive satellite sequences that
are rapidly evolving. The nucleosomes of centromeres are characterized by a
special H3-like histone (CenH3), which evolves rapidly and adaptively in
Drosophila and Arabidopsis. Most plant, animal and fungal centromeres also
bind a large protein, centromere protein C (CENP-C), that is characterized
by a single 24 amino-acid motif (CENPC motif).

Results
Whereas we find no evidence that mammalian CenH3 (CENP-A) has been evolving
adaptively, mammalian CENP-C proteins contain adaptively evolving regions
that overlap with regions of DNA-binding activity. In plants we find that
CENP-C proteins have complex duplicated regions, with conserved amino and
carboxyl termini that are dissimilar in sequence to their counterparts in
animals and fungi. Comparisons of Cenpc genes from Arabidopsis species and
from grasses revealed multiple regions that are under positive selection,
including duplicated exons in some grasses. In contrast to plants and
animals, yeast CENP-C (Mif2p) is under negative selection.

Conclusions
CENP-Cs in all plant and animal lineages examined have regions that are
rapidly and adaptively evolving. To explain these remarkable evolutionary
features for a single-copy gene that is needed at every mitosis, we propose
that CENP-Cs, like some CenH3s, suppress meiotic drive of centromeres during
female meiosis. This process can account for the rapid evolution and the
complexity of centromeric DNA in plants and animals as compared to fungi.

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