Two highly homologous ribonuclease genes expressed in mouse eosinophils identify a larger subgroup of the mammalian ribonuclease superfamily.

Abstract

Two putative ribonucleases have been isolated from the secondary granules of mouse eosinophils. Degenerate oligonucleotide primers inferred from peptide sequence data were used in reverse transcriptase-PCR reactions of bone marrow-derived cDNA. The resulting PCR product was used to screen a C57BL/6J bone marrow cDNA library, and comparisons of representative clones showed that these genes and encoded proteins are highly homologous (96% identity at the nucleotide level; 92/94% identical/similar at the amino acid level). The mouse proteins are only weakly homologous (-50%o amino acid identity) with the human eosinophil-associated ribonucleases (i.e., eosinophil-derived neurotoxin and eosinophil cationic protein) and show no sequence bias toward either human protein. Phylogenetic

Rapid Evolution of the Ribonuclease A Superfamily: Adaptive Expansion of Independent Gene Clusters in Rats and Mice

“…The cluster ribonucleases are members of the RNase A superfamily and are, to the best of our knowledge, orthologs of the EDN/ECP ribonuclease lineage described in primates . Despite the homology of each of these rat ribonucleases to members of the previously identified mouse ribonuclease (mR) gene cluster (Larson et al 1996;Batten et al 1997), the rat ribonucleases form their own (rR) cluster, as each is more closely related to another rR ribonuclease than it is to any one of the known mR ribonucleases shown. These results suggest that the rR and at least six of the eight mR ribonucleases (see Results) have evolved independently and that multiple duplication and diversification events occurred after the divergence of these two closely related rodent species.…”

“…Each sequence includes an amino terminal signal peptide, with the amino terminus of the processed form of the protein indicated as glutamine-1 (Q 1 ); glutamine-1 was found at the amino termini of the related ribonucleases mEAR-1 and -2 by direct sequencing of purified proteins (Larson et al 1996). The processed protein sequences include either 129 or 130 amino acids, each with the appropriately spaced cysteines (shaded) typical of RNase A family ribonucleases as well as the two histidines (H 13 and H 125 ) analogous to those found in the catalytic site of RNase A.…”

“…Larson et al (1996) purified ribonucleases from mouse eosinophils and ultimately identified cDNA sequences of mouse eosinophil-associated ribonuclease (mEAR) -1 and -2, ribonucleases with ∼50% amino acid sequence identity to human EDN and ECP. Southern analysis suggested the presence of multiple hybridizing species in the mouse genome (Larson et al 1996); we have since identified six related ribonuclease genes that, together with mEAR-1 and -2 form the mouse ribonuclease (mR) cluster (Batten et al 1997). These sequences define a unique, species-limited cluster within the RNase A gene family, causing us to remark on the unusual degree of duplication and diversification observed in this specific ribonuclease lineage.…”

Isolation, Characterization, and Evolutionary Divergence of Mouse RNase 6: Evidence for Unusual Evolution in Rodents

“…Human EDN (RNase 2) and ECP (RNase 3) remain among one of the most rapidly evolving genes known in primates and the orthologous mouse genes, mouse eosinophil-associated ribonucleases (Ears), have undergone rapid and divergent evolution to produce as many as 10-15 paralogous genes (Batten et al 1997;Cormier et al 2001;Larson et al 1996;McDevitt et al 2001;Singhania et al 1999;Zhang et al 2000). The pancreatic ribonuclease lineage has undergone at least two species-specific duplications, one in ruminants, resulting in pancreatic, seminal, and brain ribonucleases Sasso et al 1999), and another in the leaf-eating monkey douc langur, resulting in two distinct enzymes with differing substrate specificities and optimal pHs (Zhang et al 2002b).…”

Eosinophil-Derived Neurotoxin / RNase 2: Connecting the Past, the Present and the Future

“…The first rodent orthologs of EDN (and ECP) were identified by Larsen and colleagues [23] by direct isolation of proteins from mouse eosinophils followed by amino terminal sequencing and ultimately, gene cloning. The mouse eosinophil-associated RNases are a highly divergent cluster of individual genes that have diverged by an unusual mechanism known as rapid birthdeath followed by gene sorting [24], a mechanism that has been characterized for only a few other multi-gene families, typically those involved in generation of functional diversity (e.g.…”