title: A novel source for miR-21 expression through the alternative polyadenylation of VMP1 gene transcripts.
abstract: miR-21 is the most commonly over-expressed microRNA (miRNA) in cancer and a proven oncogene. Hsa-miR-21 is located on chromosome 17q23.2, immediately downstream of the vacuole membrane protein-1 (VMP1) gene, also known as TMEM49. VMP1 transcripts initiate ∼ 130 kb upstream of miR-21, are spliced, and polyadenylated only a few hundred base pairs upstream of the miR-21 hairpin. On the other hand, primary miR-21 transcripts (pri-miR-21) originate within the last introns of VMP1, but bypass VMP1 polyadenylation signals to include the miR-21 hairpin. Here, we report that VMP1 transcripts can also bypass these polyadenylation signals to include miR-21, thus providing a novel and independently regulated source of miR-21, termed VMP1-miR-21. Northern blotting, gene-specific RT-PCR, RNA pull-down and DNA branching assays support that VMP1-miR-21 is expressed at significant levels in a number of cancer cell lines and that it is processed by the Microprocessor complex to produce mature miR-21. VMP1 and pri-miR-21 are induced by common stimuli, such as phorbol-12-myristate-13-acetate (PMA) and androgens, but show differential responses to some stimuli such as epigenetic modifying agents. Collectively, these results indicate that miR-21 is a unique miRNA capable of being regulated by alternative polyadenylation and two independent gene promoters.
authors.affiliation: The James Buchannan Brady Urological Institute, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA. judit.ribas@mex.udl.cat
authors.forename: Judit
authors.initials: J
authors.lastname: Ribas
authors.forename: Xiaohua
authors.initials: X
authors.lastname: Ni
authors.forename: Mark
authors.initials: M
authors.lastname: Castanares
authors.forename: Minzhi M
authors.initials: MM
authors.lastname: Liu
authors.forename: David
authors.initials: D
authors.lastname: Esopi
authors.forename: Srinivasan
authors.initials: S
authors.lastname: Yegnasubramanian
authors.forename: Ronald
authors.initials: R
authors.lastname: Rodriguez
authors.forename: Joshua T
authors.initials: JT
authors.lastname: Mendell
authors.forename: Shawn E
authors.initials: SE
authors.lastname: Lupold
mesh_terms: D045744:Cell Line, Tumor; D005786:Gene Expression Regulation; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D035683:MicroRNAs / Q000235:genetics* / Q000378:metabolism; D026723:Polyadenylation; D012322:RNA Precursors / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D043244:Ribonuclease III / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: C524940:MIRN21 microRNA, human; D008565:Membrane Proteins; D035683:MicroRNAs; D012322:RNA Precursors; D012333:RNA, Messenger; C526584:VMP1 protein, human; C517918:DROSHA protein, human; D043244:Ribonuclease III