title: MetaSINEs: Broad Distribution of a Novel SINE Superfamily in Animals.
abstract: SINEs (short interspersed elements) are transposable elements that typically originate independently in each taxonomic clade (order/family). However, some SINE families share a highly similar central sequence and are thus categorized as a SINE superfamily. Although only four SINE superfamilies (CORE-SINEs, V-SINEs, DeuSINEs, and Ceph-SINEs) have been reported so far, it is expected that new SINE superfamilies would be discovered by deep exploration of new SINEs in metazoan genomes. Here we describe 15 SINEs, among which 13 are novel, that have a similar 66-bp central region and therefore constitute a new SINE superfamily, MetaSINEs. MetaSINEs are distributed from fish to cnidarians, suggesting their common evolutionary origin at least 640 Ma. Because the 3' tails of MetaSINEs are variable, these SINEs most likely survived by changing their partner long interspersed elements for retrotransposition during evolution. Furthermore, we examined the presence of members of other SINE superfamilies in bivalve genomes and characterized eight new SINEs belonging to the CORE-SINEs, V-SINEs, and DeuSINEs, in addition to the MetaSINEs. The broad distribution of bivalve SINEs suggests that at least three SINEs originated in the common ancestor of Bivalvia. Our comparative analysis of the central domains of the SINEs revealed that, in each superfamily, only a restricted region is shared among all of its members. Because the functions of the central domains of the SINE superfamilies remain unknown, such structural information of SINE superfamilies will be useful for future experimental and comparative analyses to reveal why they have been retained in metazoan genomes during evolution.
authors.affiliation: Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Midori-Ku, Yokohama, Kanagawa, Japan.
authors.forename: Hidenori
authors.initials: H
authors.lastname: Nishihara
authors.affiliation: Department of Biological, Geological and Environmental Sciences, University of Bologna, Bologna, Italy.
authors.forename: Federico
authors.initials: F
authors.lastname: Plazzi
authors.affiliation: Department of Biological, Geological and Environmental Sciences, University of Bologna, Bologna, Italy nokada@fais.or.jp marco.passamonti@unibo.it.
authors.forename: Marco
authors.initials: M
authors.lastname: Passamonti
authors.affiliation: Department of Life Sciences, National Cheng Kung University, Tainan, Taiwan Foundation for Advancement of International Science, Tsukuba, Japan nokada@fais.or.jp marco.passamonti@unibo.it.
authors.forename: Norihiro
authors.initials: N
authors.lastname: Okada
mesh_terms: D000818:Animals; D049872:Bivalvia / Q000235:genetics; D004251:DNA Transposable Elements / Q000235:genetics; D019143:Evolution, Molecular; D010802:Phylogeny; D020086:Short Interspersed Nucleotide Elements / Q000235:genetics*
chemical_list: D004251:DNA Transposable Elements
keywords: Eumetazoa; bivalves; central domain; mollusks; short interspersed elements; transposable elements