title: The human let-7a-3 locus contains an epigenetically regulated microRNA gene with oncogenic function.
abstract: MicroRNAs (miRNAs) are small noncoding RNAs that repress their target mRNAs by complementary base pairing and induction of the RNA interference pathway. It has been shown that miRNA expression can be regulated by DNA methylation and it has been suggested that altered miRNA gene methylation might contribute to human tumorigenesis. In this study, we show that the human let-7a-3 gene on chromosome 22q13.31 is associated with a CpG island. Let-7a-3 belongs to the archetypal let-7 miRNA gene family and was found to be methylated by the DNA methyltransferases DNMT1 and DNMT3B. The gene was heavily methylated in normal human tissues but hypomethylated in some lung adenocarcinomas. Let-7a-3 hypomethylation facilitated epigenetic reactivation of the gene and elevated expression of let-7a-3 in a human lung cancer cell line resulted in enhanced tumor phenotypes and oncogenic changes in transcription profiles. Our results thus identify let-7a-3 as an epigenetically regulated miRNA gene with oncogenic function and suggest that aberrant miRNA gene methylation might contribute to the human cancer epigenome.
authors.affiliation: Divisions of Epigenetics and Molecular Genome Analysis, Deutsches Krebsforschungszentrum, Im Neuenheimer Feld 580, 69120 Heidelberg, Germany.
authors.forename: Bodo
authors.initials: B
authors.lastname: Brueckner
authors.forename: Carlo
authors.initials: C
authors.lastname: Stresemann
authors.forename: Ruprecht
authors.initials: R
authors.lastname: Kuner
authors.forename: Cora
authors.initials: C
authors.lastname: Mund
authors.forename: Tanja
authors.initials: T
authors.lastname: Musch
authors.forename: Michael
authors.initials: M
authors.lastname: Meister
authors.forename: Holger
authors.initials: H
authors.lastname: Sültmann
authors.forename: Frank
authors.initials: F
authors.lastname: Lyko
mesh_terms: D000230:Adenocarcinoma / Q000235:genetics; D000236:Adenoma / Q000235:genetics; D015179:Colorectal Neoplasms / Q000235:genetics; D019175:DNA Methylation; D045325:HCT116 Cells; D006801:Humans; D008175:Lung Neoplasms / Q000235:genetics; D035683:MicroRNAs / Q000235:genetics* / Q000378:metabolism; D009369:Neoplasms / Q000235:genetics*; D009857:Oncogenes; D014162:Transfection
chemical_list: D035683:MicroRNAs; C487931:mirnlet7 microRNA, human