title: Antagonistic role of hnRNP A1 and KSRP in the regulation of let-7a biogenesis.
abstract: The pluripotency-promoting proteins Lin28a and Lin28b act as post-transcriptional repressors of let-7 miRNA biogenesis in undifferentiated embryonic stem cells. The levels of mature let-7a differ substantially in cells lacking Lin28 expression, indicating the existence of additional mechanism(s) of post-transcriptional regulation. Here, we present evidence supporting a role for heteronuclear ribonucleoprotein A1 (hnRNP A1) as a negative regulator of let-7a. HnRNP A1 binds the conserved terminal loop of pri-let-7a-1 and inhibits its processing by Drosha. Levels of mature let-7a negatively correlate with hnRNP A1 levels in somatic cell lines. Furthermore, hnRNP A1 depletion increased pri-let-7a-1 processing by cell extracts, whereas its ectopic expression decreased let-7a production in vivo. Finally, hnRNP A1 binding to let-7a interferes with the binding of KSRP, which is known to promote let-7a biogenesis. We propose that hnRNP A1 and KSRP have antagonistic roles in the post-transcriptional regulation of let-7a expression.
authors.affiliation: Medical Research Council Human Genetics Unit, Institute of Genetics and Molecular Medicine, Western General Hospital, Edinburgh, UK.
authors.forename: Gracjan
authors.initials: G
authors.lastname: Michlewski
authors.forename: Javier F
authors.initials: JF
authors.lastname: Cáceres
mesh_terms: D001483:Base Sequence; D001667:Binding, Competitive; D045744:Cell Line, Tumor; D018983:DNA Footprinting; D015972:Gene Expression Regulation, Neoplastic; D049452:Green Fluorescent Proteins / Q000378:metabolism; D000076245:Heterogeneous Nuclear Ribonucleoprotein A1; D034481:Heterogeneous-Nuclear Ribonucleoprotein Group A-B / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D035683:MicroRNAs / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics; D008954:Models, Biological; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D011485:Protein Binding; D012323:RNA Processing, Post-Transcriptional; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D043244:Ribonuclease III / Q000378:metabolism; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*
chemical_list: D000076245:Heterogeneous Nuclear Ribonucleoprotein A1; D034481:Heterogeneous-Nuclear Ribonucleoprotein Group A-B; C105789:KHSRP protein, human; D035683:MicroRNAs; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; C487931:mirnlet7 microRNA, human; D049452:Green Fluorescent Proteins; C517918:DROSHA protein, human; D043244:Ribonuclease III