MBE Advance Access published online on October 16, 2007
Molecular Biology and Evolution, doi:10.1093/molbev/msm221
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Research Article |
Convergent Domestication of pogo-Like Transposases Into Centromere-Binding Proteins in Fission Yeast and Mammals
Department of Biology, University of Texas, Arlington, TX 76019, USA
Corresponding author: Cédric Feschotte, Department of Biology, Box 19498, University of Texas, Arlington, TX 76019. Phone 817-272-2426. Fax (817) 272 2855. cedric{at}uta.edu
Received for publication July 25, 2007. Revision received September 15, 2007. Accepted for publication October 2, 2007.
The mammalian centromeric protein CENP-B shares significant sequence similarity with three proteins in fission yeast (Abp1, Cbh1 and Cbh2) that also bind centromeres and have essential function for chromosome segregation and centromeric heterochromatin formation. Each of these proteins displays extensive sequence similarity with pogo-like transposases, which have been previously identified in the genomes of various insects and vertebrates, in the protozoan Entamoeba and in plants. Based on this distribution, it has been proposed that the mammalian and fission yeast centromeric proteins are derived from ‘domesticated’ pogo-like transposons. Here we took advantage of the vast amount of sequence information that has become recently available for a wide range of fungal and animal species to investigate the origin of the mammalian CENP-B and yeast CENP-B-like genes. A highly conserved ortholog of CENP-B was detected in 31 species of mammals, including opossum and platypus, but was absent from all non-mammalian species represented in the databases. Similarly, no ortholog of the fission yeast centromeric proteins was identified in any of the various fungal genomes currently available. In contrast, we discovered a plethora of novel pogo-like transposons in diverse invertebrates and vertebrates and in several filamentous fungi. Phylogenetic analysis revealed that the mammalian and fission yeast CENP-B proteins fall into two distinct monophyletic clades, each of which includes a different set of pogo-like transposons. These results are most parsimoniously explained by independent domestication events of pogo-like transposases into centromeric proteins in the mammalian and fission yeast lineages, a case of ‘convergent domestication’. These findings highlight the propensity of transposases to give rise to new host proteins and the potential of transposons as sources of genetic innovation.
Key Words: exaptation • transposon domestication • convergence • centromeres • CENP-B • Abp1
1 these authors contributed equally to this work
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