title: kangaroo, a mobile element from Volvox carteri, is a member of a newly recognized third class of retrotransposons.
abstract: Retrotransposons play an important role in the evolution of genomic structure and function. Here we report on the characterization of a novel retrotransposon called kangaroo from the multicellular green alga, Volvox carteri. kangaroo elements are highly mobile and their expression is developmentally regulated. They probably integrate via double-stranded, closed-circle DNA intermediates through the action of an encoded recombinase related to the lambda-site-specific integrase. Phylogenetic analysis indicates that kangaroo elements are closely related to other unorthodox retrotransposons including PAT (from a nematode), DIRS-1 (from Dictyostelium), and DrDIRS1 (from zebrafish). PAT and kangaroo both contain split direct repeat (SDR) termini, and here we show that DIRS-1 and DrDIRS1 elements contain terminal features structurally related to SDRs. Thus, these mobile elements appear to define a third class of retrotransposons (the DIRS1 group) that are unified by common structural features, genes, and integration mechanisms, all of which differ from those of LTR and conventional non-LTR retrotransposons.
authors.affiliation: Department of Biology, Washington University, Saint Louis, Missouri 63130, USA. len.duncan@cumbre.net
authors.forename: Leonard
authors.initials: L
authors.lastname: Duncan
authors.forename: Kristine
authors.initials: K
authors.lastname: Bouckaert
authors.forename: Fay
authors.initials: F
authors.lastname: Yeh
authors.forename: David L
authors.initials: DL
authors.lastname: Kirk
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D000460:Chlorophyta / Q000235:genetics* / Q000254:growth & development; D004254:DNA Nucleotidyltransferases / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D019143:Evolution, Molecular; D018507:Gene Expression Regulation, Developmental; D019426:Integrases / Q000235:genetics; D008957:Models, Genetic; D008969:Molecular Sequence Data; D045522:Recombinases; D018626:Retroelements / Q000235:genetics*; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D013045:Species Specificity
chemical_list: D018076:DNA, Complementary; D045522:Recombinases; D018626:Retroelements; D004254:DNA Nucleotidyltransferases; D019426:Integrases