Nucleic Acids Research Advance Access published online on March 6, 2009
Nucleic Acids Research, doi:10.1093/nar/gkp123
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The RNA-binding protein HuR regulates DNA methylation through stabilization of DNMT3b mRNA
1Cancer Epigenetics Laboratory, Molecular Pathology Program, Spanish National Cancer Research Centre (CNIO), 28029 Madrid, Spain, 2Laboratory of Cellular and Molecular Biology, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, USA, 3Department of Histology, Granada University and Hospital Clinico Foundation, Granada, 4Institucio Catalana de Recerca i Estudis Avançats (ICREA), 08010 Barcelona and 5Cancer Epigenetics and Biology Program (PEBC), Catalan Institute of Oncology (ICO), Institut d’Investigacio Biomedica de Bellvitge (IDIBELL), 08907 L’Hospitalet, Barcelona, Catalonia, Spain
*To whom correspondence should be addressed. Tel: +(34) 917 328 000; Fax: +(34) 912 246 980; Email: ilsilanes{at}cnio.es
Received December 4, 2008. Revised February 13, 2009. Accepted February 14, 2009.
The molecular basis underlying the aberrant DNA-methylation patterns in human cancer is largely unknown. Altered DNA methyltransferase (DNMT) activity is believed to contribute, as DNMT expression levels increase during tumorigenesis. Here, we present evidence that the expression of DNMT3b is post-transcriptionally regulated by HuR, an RNA-binding protein that stabilizes and/or modulates the translation of target mRNAs. The presence of a putative HuR-recognition motif in the DNMT3b 3'UTR prompted studies to investigate if this transcript associated with HuR. The interaction between HuR and DNMT3b mRNA was studied by immunoprecipitation of endogenous HuR ribonucleoprotein complexes followed by RT–qPCR detection of DNMT3b mRNA, and by in vitro pulldown of biotinylated DNMT3b RNAs followed by western blotting detection of HuR. These studies revealed that binding of HuR stabilized the DNMT3b mRNA and increased DNMT3b expression. Unexpectedly, cisplatin treatment triggered the dissociation of the [HuR-DNMT3b mRNA] complex, in turn promoting DNMT3b mRNA decay, decreasing DNMT3b abundance, and lowering the methylation of repeated sequences and global DNA methylation. In summary, our data identify DNMT3b mRNA as a novel HuR target, present evidence that HuR affects DNMT3b expression levels post-transcriptionally, and reveal the functional consequences of the HuR-regulated DNMT3b upon DNA methylation patterns.
Correspondence may also be addressed to Manel Esteller. Tel: +(34) 93 260 7253; Fax: +(34) 93 260 7219; Email: mesteller{at}iconcologia.net