title: Molluscan mobile elements similar to the vertebrate Recombination-Activating Genes.
abstract: Animal genomes contain approximately 20,000 genes. Additionally millions of genes for antigen receptors are generated in cells of the immune system from the sets of separate gene segments by a mechanism known as the V(D)J somatic recombination. The components of the V(D)J recombination system, Recombination-Activating Gene proteins (RAG1 and RAG2) and recombination signal sequence (RSS), are thought to have "entered" the vertebrate genome as a hypothetical "RAG transposon". Recently discovered mobile elements have terminal inverted repeats (TIRs) similar to RSS and may encode proteins with a different degree of similarity to RAG1. We describe a novel N-RAG-TP transposon identified from the sea slug Aplysia californica that encodes a protein similar to the N-terminal part of RAG1 in vertebrates. This refines the "RAG transposon" hypothesis and allows us to propose a scenario for V(D)J recombination machinery evolution from a relic transposon related to the existing mobile elements N-RAG-TP, Chapaev, and Transib.
authors.affiliation: Institute for Information Transmission Problems, Russian Academy of Science, 127994 Moscow, Russia.
authors.forename: Yuri
authors.initials: Y
authors.lastname: Panchin
authors.forename: Leonid L
authors.initials: LL
authors.lastname: Moroz
mesh_terms: D000818:Animals; D001048:Aplysia / Q000235:genetics*; D001483:Base Sequence; D004251:DNA Transposable Elements / Q000235:genetics*; D019143:Evolution, Molecular; D018965:Frameshifting, Ribosomal; D015321:Gene Rearrangement; D018398:Homeodomain Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D014176:Protein Biosynthesis / Q000235:genetics
chemical_list: D004251:DNA Transposable Elements; D018398:Homeodomain Proteins; C064658:RAG-1 protein