Turkey and chicken interleukin-2 cross-react in in vitro proliferation assays despite limited amino acid sequence identity.
We cloned the cDNA of turkey interleukin-2 (IL-2), initially using oligonucleotide primers based on the sequence of the chicken IL-2 gene. Compared with the only other cytokines available for comparison, the interferons (IFN), the coding regions of the turkey and chicken IL-2 genes are much less conserved (86.24% nucleotide identical and 69.93% amino acid identical). The lack of nucleotide conservation was spread across the entire length of the coding region. In comparison, the promoters of the two avian IL-2 genes shared a high degree of identity (95.71% identical over 380 nucleotides). Phylogenetic analysis shows that turkey and chicken IL-2 have diverged to a greater extent than IL-2 from closely related mammalian species. Surprisingly, considering the low level of amino acid identity, including residues known to be important in binding the IL-2 receptor in mammalian species, both turkey and chicken IL-2 cross-react in functional assays.
Lawson
S
S
Institute for Animal Health, Compton, Berkshire, UK. michelle.lawson@bbsrc.ac.uk
Rothwell
L
L
Kaiser
P
P
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002645:Chickens / Q000235:genetics* / Q000276:immunology*; D003001:Cloning, Molecular; D003429:Cross Reactions; D017931:DNA Primers / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D066298:In Vitro Techniques; D007376:Interleukin-2 / Q000737:chemistry / Q000235:genetics* / Q000276:immunology*; D008969:Molecular Sequence Data; D010802:Phylogeny; D017433:Protein Structure, Secondary; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D013045:Species Specificity; D014422:Turkeys / Q000235:genetics* / Q000276:immunology*
D017931:DNA Primers; D018076:DNA, Complementary; D007376:Interleukin-2