The human let-7a-3 locus contains an epigenetically regulated microRNA gene with oncogenic function.
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.
Brueckner
Bodo
B
Divisions of Epigenetics and Molecular Genome Analysis, Deutsches Krebsforschungszentrum, Im Neuenheimer Feld 580, 69120 Heidelberg, Germany.
Stresemann
Carlo
C
Kuner
Ruprecht
R
Mund
Cora
C
Musch
Tanja
T
Meister
Michael
M
Sültmann
Holger
H
Lyko
Frank
F
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
D035683:MicroRNAs; C487931:mirnlet7 microRNA, human