The Oncogene PDRG1 Is an Interaction Target of Methionine Adenosyltransferases

PLoS One. 2016 Aug 22;11(8):e0161672. doi: 10.1371/journal.pone.0161672. eCollection 2016.

Abstract

Methionine adenosyltransferases MAT I and MAT III (encoded by Mat1a) catalyze S-adenosylmethionine synthesis in normal liver. Major hepatic diseases concur with reduced levels of this essential methyl donor, which are primarily due to an expression switch from Mat1a towards Mat2a. Additional changes in the association state and even in subcellular localization of these isoenzymes are also detected. All these alterations result in a reduced content of the moderate (MAT I) and high Vmax (MAT III) isoenzymes, whereas the low Vmax (MAT II) isoenzyme increases and nuclear accumulation of MAT I is observed. These changes derive in a reduced availability of cytoplasmic S-adenosylmethionine, together with an effort to meet its needs in the nucleus of damaged cells, rendering enhanced levels of certain epigenetic modifications. In this context, the putative role of protein-protein interactions in the control of S-adenosylmethionine synthesis has been scarcely studied. Using yeast two hybrid and a rat liver library we identified PDRG1 as an interaction target for MATα1 (catalytic subunit of MAT I and MAT III), further confirmation being obtained by immunoprecipitation and pull-down assays. Nuclear MATα interacts physically and functionally with the PDRG1 oncogene, resulting in reduced DNA methylation levels. Increased Pdrg1 expression is detected in acute liver injury and hepatoma cells, together with decreased Mat1a expression and nuclear accumulation of MATα1. Silencing of Pdrg1 expression in hepatoma cells alters their steady-state expression profile on microarrays, downregulating genes associated with tumor progression according to GO pathway analysis. Altogether, the results unveil the role of PDRG1 in the control of the nuclear methylation status through methionine adenosyltransferase binding and its putative collaboration in the progression of hepatic diseases.

MeSH terms

  • Animals
  • CHO Cells
  • COS Cells
  • Cell Line, Tumor
  • Chlorocebus aethiops
  • Cricetulus
  • DNA Methylation
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • Epigenesis, Genetic*
  • Gene Expression Profiling
  • Gene Expression Regulation, Enzymologic*
  • Gene Library
  • HEK293 Cells
  • Hepatocytes / enzymology*
  • Hepatocytes / pathology
  • Humans
  • Isoenzymes / genetics
  • Isoenzymes / metabolism
  • Liver / enzymology
  • Liver / pathology
  • Male
  • Methionine Adenosyltransferase / genetics
  • Methionine Adenosyltransferase / metabolism*
  • Oncogene Proteins / genetics
  • Oncogene Proteins / metabolism*
  • Oncogenes
  • Protein Interaction Mapping
  • Rats
  • Rats, Wistar
  • S-Adenosylmethionine / metabolism*
  • Two-Hybrid System Techniques

Substances

  • DNA-Binding Proteins
  • Isoenzymes
  • Oncogene Proteins
  • Pdrg1 protein, rat
  • S-Adenosylmethionine
  • Methionine Adenosyltransferase

Grant support

CP was a postdoctoral fellow of the UNAM-CSIC program and ER was supported by RCMN C03/08 and PI05/056. This work was supported by grants of the Ministerio de Economía y Competitividad (BFU2005-00050, BFU2008-00666, BFU2009-08977), and the Instituto de Salud Carlos III (RCMN C03/08 and PI05/0563). The authors declare that there are no competing interests. The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript.