MBE Advance Access published online on June 16, 2004
Molecular Biology and Evolution, doi:10.1093/molbev/msh190
Molecular Biology and Evolution © Society for Molecular Biology and Evolution 2004; all rights reserved
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1 Dipartimento di Anatomia Patologica e Genetica, Sezione di Genetica, Via Amendola 165/A, 70126 Bari
* To whom correspondence should be addressed. E-mail: raffaella.meneveri{at}unimib.it.
In the present paper we report studies on the evolutionary history of beta satellite repeats (BSR) in primates. In the orangutan genome, the bulk of BSR sequences was found organized as very short stretches of approx. 100-170bp, embedded in a 60-80kb duplicated DNA segment. The estimated copy number of the duplicon carrying BSR sequences ranges from 70 to 100 per orangutan haploid genome. In both macaque and gibbon the duplicon mapped to a single chromosomal region at the boundary of the rDNA on the marker chromosome (chromosome 13 and 12, respectively). However, only in the gibbon the duplicon comprised 100bp of beta satellite. Thus, the ancestral copy of the duplicon appeared in Old World Monkeys (
Original Articles
Evolution of Beta Satellite DNA Sequences: Evidence for Duplication-Mediated Repeat Amplification and Spreading
2 Dipartimento di Biologia e Genetica per le Scienze Mediche, Via Viotti 3/5, 20133 Milano
3 Dipartimento di Medicina Sperimentale, Ambientale e Biotecnologie Mediche, Via Cadore 48, 20052 Monza, Italy
Abstract 
25-35 Mya ago), whereas the prototype of beta satellite repeats took place in a gibbon ancestor, after apes/Old World Monkeys divergence (25 Mya ago). Subsequently, a burst in spreading of the duplicon carrying the beta satellite was observed in the orangutan, after lesser apes divergence from the great apes-humans lineage (18 Mya ago). The analysis of the orangutan genome also indicated the existence of two variants of the duplication, differing for the length (100 or 170bp) of beta satellite repeats. The latter organization was probably generated by non-homologous recombination between two 100bp repeated regions, and it likely led to the duplication of the single Sau3A site present in the 100bp variant, generating the prototype of Sau3A 68bp beta satellite tandem organization. The two variants of the duplication, although with a different ratio, characterize the hominoid genomes from the orangutan to humans, preferentially involving acrocentric chromosomes. At variance to alpha satellite, which appeared before the divergence of New and Old World Monkeys, the beta satellite evolutionary history began in apes ancestor, where we have first documented a low-copy, non duplicated BSR sequence. The first step of BSR amplification and spreading occurred, most likely, because the BSR was part of a large duplicon, which underwent a burst dispersal in great apes ancestor after lesser apes branching. Then, after orangutan divergence, BSR acquired the clustered structural organization typical of satellite DNA.
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