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Nucleic Acids Res. 2012 Aug;40(14):6821-33. doi: 10.1093/nar/gks308. Epub 2012 Apr 13.

A novel source for miR-21 expression through the alternative polyadenylation of VMP1 gene transcripts.

Author information

1
The James Buchannan Brady Urological Institute, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA. judit.ribas@mex.udl.cat

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.

PMID:
22505577
PMCID:
PMC3413119
DOI:
10.1093/nar/gks308
[Indexed for MEDLINE]
Free PMC Article

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