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Journal of Molecular Evolution

, Volume 51, Issue 3, pp 234–244 | Cite as

Fast Evolution of Interleukin-2 in Mammals and Positive Selection in Ruminants

  • Dominique  Zelus
  • Marc  Robinson-Rechavi
  • Myriam  Delacre
  • Claude  Auriault
  • Vincent  Laudet

Abstract.

Interleukin-2 (IL-2) is a cytokine involved in induction and regulation of the immune response in mammals. There have been numerous reports about the search for IL-2 in species other than mammals, and recently an IL-2-like gene has been isolated in chicken. Using PCR, we searched for IL-2 gene sequences in a wide variety of mammals, including marsupials and monotremes, as well as in birds. Although we can readily amplify IL-2 gene fragments in placental mammals, no amplification was obtained in other species. This is best explained by very high substitution rates. This suggest that strategies to isolate IL-2 homologous genes outside mammals should involve functional assays, as for the chicken gene, and not hybridization-based techniques. Nonsynonymous substitution rates are especially high in ruminants, due to positive selection acting on regions important in term of structure-function. We suggest that, although globally similar, the immune response of various mammals is not identical, mainly at the level of cytokine-mediated regulations.

Key words: Adaptation — Amino acid properties — Interleukin-2 — Ka:Ks ratio — Mammals — Molecular clock — Nonsynonymous substitution — Positive selection — Protein evolution 

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Copyright information

© Springer-Verlag New York Inc. 2000

Authors and Affiliations

  • Dominique  Zelus
    • 1
  • Marc  Robinson-Rechavi
    • 1
  • Myriam  Delacre
    • 2
  • Claude  Auriault
    • 2
  • Vincent  Laudet
    • 1
  1. 1.UMR 5665 du CNRS, Ecole Normale Supérieure de Lyon, 46 Allée d'Italie, 69364 Lyon Cedex 07, FranceFR
  2. 2.UMR 8527 du CNRS, Institut de Biologie de Lille, Institut Pasteur de Lille, 1 rue du Professeur Calmette, 59019 Lille Cedex, FranceFR

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