title: Conservation of the sequence and temporal expression of let-7 heterochronic regulatory RNA.
abstract: Two small RNAs regulate the timing of Caenorhabditis elegans development. Transition from the first to the second larval stage fates requires the 22-nucleotide lin-4 RNA, and transition from late larval to adult cell fates requires the 21-nucleotide let-7 RNA. The lin-4 and let-7 RNA genes are not homologous to each other, but are each complementary to sequences in the 3' untranslated regions of a set of protein-coding target genes that are normally negatively regulated by the RNAs. Here we have detected let-7 RNAs of approximately 21 nucleotides in samples from a wide range of animal species, including vertebrate, ascidian, hemichordate, mollusc, annelid and arthropod, but not in RNAs from several cnidarian and poriferan species, Saccharomyces cerevisiae, Escherichia coli or Arabidopsis. We did not detect lin-4 RNA in these species. We found that let-7 temporal regulation is also conserved: let-7 RNA expression is first detected at late larval stages in C. elegans and Drosophila, at 48 hours after fertilization in zebrafish, and in adult stages of annelids and molluscs. The let-7 regulatory RNA may control late temporal transitions during development across animal phylogeny.
authors.affiliation: Department of Molecular Biology, Massachusetts General Hospital, Harvard Medical School, Boston 02114, USA.
authors.forename: A E
authors.initials: AE
authors.lastname: Pasquinelli
authors.forename: B J
authors.initials: BJ
authors.lastname: Reinhart
authors.forename: F
authors.initials: F
authors.lastname: Slack
authors.forename: M Q
authors.initials: MQ
authors.lastname: Martindale
authors.forename: M I
authors.initials: MI
authors.lastname: Kuroda
authors.forename: B
authors.initials: B
authors.lastname: Maller
authors.forename: D C
authors.initials: DC
authors.lastname: Hayward
authors.forename: E E
authors.initials: EE
authors.lastname: Ball
authors.forename: B
authors.initials: B
authors.lastname: Degnan
authors.forename: P
authors.initials: P
authors.lastname: Müller
authors.forename: J
authors.initials: J
authors.lastname: Spring
authors.forename: A
authors.initials: A
authors.lastname: Srinivasan
authors.forename: M
authors.initials: M
authors.lastname: Fishman
authors.forename: J
authors.initials: J
authors.lastname: Finnerty
authors.forename: J
authors.initials: J
authors.lastname: Corbo
authors.forename: M
authors.initials: M
authors.lastname: Levine
authors.forename: P
authors.initials: P
authors.lastname: Leahy
authors.forename: E
authors.initials: E
authors.lastname: Davidson
authors.forename: G
authors.initials: G
authors.lastname: Ruvkun
mesh_terms: D000328:Adult; D000818:Animals; D001483:Base Sequence; D017173:Caenorhabditis elegans / Q000235:genetics*; D017124:Conserved Sequence; D004331:Drosophila melanogaster; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D008969:Molecular Sequence Data; D010802:Phylogeny; D012313:RNA / Q000737:chemistry / Q000235:genetics*; D018510:RNA, Helminth; D013045:Species Specificity
chemical_list: D018510:RNA, Helminth; D012313:RNA