title: Appearance and disappearance of Syk family protein-tyrosine kinase genes during metazoan evolution.
abstract: Syk family protein-tyrosine kinases are essential components of immunoreceptor signaling in mammalian lymphocytes. The absence of Syk genes from the Caenorhabditis elegans genome suggests that this kinase family is of recent evolutionary origin. Surprisingly, we have found that Hydra vulgaris, a member of the early diverging animal phylum Cnidaria, contains a gene encoding a Syk kinase. Phylogenetic analysis indicates that a single Syk family gene was present in animals prior to the gene duplication that gave rise to Syk and ZAP-70, the two mammalian Syk family genes. C. elegans also lacks a Shark protein-tyrosine kinase gene, which we show is a member of a sister group to the Syk family. We conclude that both Syk and Shark genes were lost from the genome of an ancestor of C. elegans. This natural gene knockout result indicates that neither Syk nor Shark kinases are essential for processes held in common between the nematode and other metazoans. The Hydra Syk gene is expressed in epithelial cells, a site consistent with a role for Hydra Syk in recognition of foreign cells.
authors.affiliation: Department of Biological Chemistry, University of California, Irvine 92697-1700, USA. resteele@uci.edu
authors.forename: R E
authors.initials: RE
authors.lastname: Steele
authors.forename: N A
authors.initials: NA
authors.lastname: Stover
authors.forename: M
authors.initials: M
authors.lastname: Sakaguchi
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D004792:Enzyme Precursors / Q000235:genetics*; D019143:Evolution, Molecular; D006829:Hydra / Q000201:enzymology / Q000235:genetics*; D017403:In Situ Hybridization; D047908:Intracellular Signaling Peptides and Proteins; D008969:Molecular Sequence Data; D010802:Phylogeny; D011505:Protein-Tyrosine Kinases / Q000235:genetics*; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D000072377:Syk Kinase
chemical_list: D018076:DNA, Complementary; D004792:Enzyme Precursors; D047908:Intracellular Signaling Peptides and Proteins; D011505:Protein-Tyrosine Kinases; D000072377:Syk Kinase