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Open Access Research article

RPS4Y gene family evolution in primates

Olga Andrés12, Thomas Kellermann23, Francesc López-Giráldez1, Julio Rozas4, Xavier Domingo-Roura1 and Montserrat Bosch12*

Author Affiliations

1 Genètica de la Conservació Animal, Institut de Recerca i Tecnologia Agroalimentàries, Crta. de Cabrils km2, 08348 Cabrils, Spain

2 Departament de Ciències Experimentals i de la Salut, Universitat Pompeu Fabra, Dr. Aiguader 80, 08003 Barcelona, Spain

3 Institut für Immungenetik, Charité-Universitätsmedizin Berlin, Campus Benjamin Franklin, Freie Universität Berlin, Thielallee 73, 14195 Berlin, Germany

4 Departament de Genètica, Universitat de Barcelona, Av. Diagonal 645, 08028 Barcelona, Spain

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BMC Evolutionary Biology 2008, 8:142  doi:10.1186/1471-2148-8-142

Published: 13 May 2008

Abstract

Backgound

The RPS4 gene codifies for ribosomal protein S4, a very well-conserved protein present in all kingdoms. In primates, RPS4 is codified by two functional genes located on both sex chromosomes: the RPS4X and RPS4Y genes. In humans, RPS4Y is duplicated and the Y chromosome therefore carries a third functional paralog: RPS4Y2, which presents a testis-specific expression pattern.

Results

DNA sequence analysis of the intronic and cDNA regions of RPS4Y genes from species covering the entire primate phylogeny showed that the duplication event leading to the second Y-linked copy occurred after the divergence of New World monkeys, about 35 million years ago. Maximum likelihood analyses of the synonymous and non-synonymous substitutions revealed that positive selection was acting on RPS4Y2 gene in the human lineage, which represents the first evidence of positive selection on a ribosomal protein gene. Putative positive amino acid replacements affected the three domains of the protein: one of these changes is located in the KOW protein domain and affects the unique invariable position of this motif, and might thus have a dramatic effect on the protein function.

Conclusion

Here, we shed new light on the evolutionary history of RPS4Y gene family, especially on that of RPS4Y2. The results point that the RPS4Y1 gene might be maintained to compensate gene dosage between sexes, while RPS4Y2 might have acquired a new function, at least in the lineage leading to humans.