Aberrant DNA Methylation of Ribosomal RNA Genes in Human Cancer
Stefanie Teschler, Antje M Richter, Benedikt Linder and Reinhard H Dammann*
Institute for Genetics, Justus-Liebig-University Giessen, Heinrich Buff Ring 58-62, Giessen D-35392, Germany
- *Corresponding Author:
- Reinhard H Dammann
Institute for Genetics, Justus-Liebig-University
Giessen Heinrich-Buff-Ring 58-62 and Marburg Lung Center
Member of the German Center for Lung Research, D-35392 Giessen, Germany
E-mail: [email protected] gen.bio.uni-giessen.de
Received date: June 20, 2015; Accepted date: July 20, 2015; Published date: July 27, 2015
Citation: Teschler S, Richter AM, Linder B, Dammann RH (2015) Aberrant DNA Methylation of Ribosomal RNA Genes in Human Cancer. Mol Biol 4:128. doi:10.4172/2168-9547.1000128
Copyright: © 2015 Teschler S, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Aberrant regulation of rRNA genes has been reported in human cancers. The aim of this study was to analyze the epigenetic regulation of rRNA genes in lung cancer and to correlate methylation levels of the promoter, 18S and 28S regions with different chromatin states. Here we report, that methylation of rDNA ranged from 10% to 30% at individual CpG sites in the promoter region. In primary lung cancers a 1.2-fold increased rDNA methylation was observed at 19 analyzed CpGs (p < 0.001). Moreover, we report an increased methylation level of rDNA towards the 28S region of rRNA genes. This hypermethylation was more pronounced in cancer cell lines compared to primary tissue. To analyze the methylation status of protein-enriched rDNA, we utilized a technique that combines ChIP and bisulfite sequencing. Pol I- and CTCF-associated rDNA exhibited reduced methylation levels compared to global rDNA. Histone H1- associated promoter regions showed a 1.5-fold increase in methylation levels compared to H3-associated rDNA. In DNMT1 knock out cells a strong reduction of methylation of 18S and 28S regions was found in comparison to wild type HCT116 cells (2.7- and 1.4-fold reduction, respectively). In double DNMT1 and DNMT3B knock out cells no substantial rDNA methylation was detected. Independent of this hypomethylation, 28S level and number of rDNA repeats were constant in wild type, single knock out and double knockout HCT116 cells. Our data suggest that aberrant methylation of rDNA occurs in human cancer and that rRNA gene activity can be modulated in a constant manner independent of the level of methylated rDNA.