Journal
GENOMICS
Volume 85, Issue 2, Pages 208-220Publisher
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.ygeno.2004.10.008
Keywords
RNase; gene family; eosinophil-associated ribonuclease; angiogenin; positive selection; gene sorting
Funding
- NIGMS NIH HHS [GM67030] Funding Source: Medline
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The RNase A superfamily has been important in biochemical, structural, and evolutionary studies and is believed to be the sole vertebratespecific enzyme family. To understand the origin and diversification of the superfamily, we here determine its entire repertoire in the sequenced genomes of human, mouse, rat, and chicken. We report a previously unnoticed gene cluster in mouse chromosome 10 and a number of new genes, including mammalian RNases 11-13, which are close relatives of the recently identified RNases 9 and 10. Gene expression data imply male-reproductive functions for RNascs 9-13, although their sequences suggest the lack of ribonucleolytic activities. In contrast to the presence of 13-20 functional genes in mammals, chicken has only 3 RNase genes, which are evolutionarily close to mammalian RNase 5, like other nonmammalian RNases. This and other evidence suggests that the RNase A superfamily originated from an RNase 5-like gene and expanded in mammals. Together with the fact that multiple lineages of the superfamily, including RNases 2, 3, 5, and 7, have antipathogenic activities, we suggest that the superfamily started off as a host-defense mechanism in vertebrates. Consistent with this hypothesis, all members of the superfamily exhibit high rates of amino acid substitution as is commonly observed in immunity genes. (C) 2004 Elsevier Inc. All rights reserved.
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