title: Identification and Validation of Evolutionarily Conserved Unusually Short Pre-mRNA Introns in the Human Genome.
abstract: According to the length distribution of human introns, there is a large population of short introns with a threshold of 65 nucleotides (nt) and a peak at 85 nt. Using human genome and transcriptome databases, we investigated the introns shorter than 66 nt, termed ultra-short introns, the identities of which are scarcely known. Here, we provide for the first time a list of bona fide human ultra-short introns, which have never been characterized elsewhere. By conducting BLAST searches of the databases, we screened 22 introns (37-65 nt) with conserved lengths and sequences among closely related species. We then provide experimental and bioinformatic evidence for the splicing of 15 introns, of which 12 introns were remarkably G-rich and 9 introns contained completely inefficient splice sites and/or branch sites. These unorthodox characteristics of ultra-short introns suggest that there are unknown splicing mechanisms that differ from the well-established mechanism.
authors.affiliation: Division of Gene Expression Mechanism, Institute for Comprehensive Medical Science, Fujita Health University, Toyoake, Aichi 470-1192, Japan. mshimada@fujita-hu.ac.jp.
authors.forename: Makoto K
authors.initials: MK
authors.lastname: Shimada
authors.affiliation: Division of Gene Expression Mechanism, Institute for Comprehensive Medical Science, Fujita Health University, Toyoake, Aichi 470-1192, Japan.|Matsunami Research Park (Sosai-kouseikai), 10 Izumi-cho, Kasamatsu-cho, Hashima-gun, Gifu 501-6061, Japan.
authors.forename: Noriko
authors.initials: N
authors.lastname: Sasaki-Haraguchi
authors.affiliation: Division of Gene Expression Mechanism, Institute for Comprehensive Medical Science, Fujita Health University, Toyoake, Aichi 470-1192, Japan. mayeda@fujita-hu.ac.jp.
authors.forename: Akila
authors.initials: A
authors.lastname: Mayeda
mesh_terms: D001483:Base Sequence; D017124:Conserved Sequence; D019143:Evolution, Molecular; D020862:GC Rich Sequence; D015894:Genome, Human; D006801:Humans; D007438:Introns; D008969:Molecular Sequence Data; D012326:RNA Splicing; D012333:RNA, Messenger / Q000235:genetics*; D059467:Transcriptome
chemical_list: D012333:RNA, Messenger