title: Trans-splicing and polyadenylation of let-7 microRNA primary transcripts.
abstract: Members of the microRNA (miRNA) class of 22-nucleotide RNAs regulate the expression of target genes that contain sequences of antisense complementarity. Maturation of miRNAs involves cleavage of longer primary transcripts, but little is yet understood about how miRNA genes are transcribed and enter the processing pathway. We find that relatively long, polyadenylated transcripts encoded by the Caenorhabditis elegans let-7 gene undergo trans-splicing to the spliced leader 1 (SL1) RNA. Deletions, including removal of the trans-splice site, upstream of mature let-7 sequence result in stable accumulation of primary transcripts and compromised production of mature let-7 RNA in vivo. Our data show that multiple steps of let-7 miRNA biogenesis can be uncoupled, allowing for complex regulation in the production of a functional miRNA. Finally, the observation that let-7 primary transcripts undergo splicing highlights the importance of identifying the sequence of endogenous pri-miRNA substrates recognized by the cellular processing machinery.
authors.affiliation: Department of Biology, University of California, San Diego, La Jolla, CA 92093, USA.
authors.forename: John
authors.initials: J
authors.lastname: Bracht
authors.forename: Shaun
authors.initials: S
authors.lastname: Hunter
authors.forename: Rachel
authors.initials: R
authors.lastname: Eachus
authors.forename: Phillip
authors.initials: P
authors.lastname: Weeks
authors.forename: Amy E
authors.initials: AE
authors.lastname: Pasquinelli
mesh_terms: D000818:Animals; D001483:Base Sequence; D029742:Caenorhabditis elegans Proteins / Q000235:genetics*; D017238:Genes, Helminth; D035683:MicroRNAs / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D026723:Polyadenylation; D018510:RNA, Helminth / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D043244:Ribonuclease III / Q000378:metabolism; D020040:Trans-Splicing; D014158:Transcription, Genetic
chemical_list: D029742:Caenorhabditis elegans Proteins; D035683:MicroRNAs; D018510:RNA, Helminth; C474488:let-7 microRNA, C elegans; D043244:Ribonuclease III