title: A metabolic throttle regulates the epigenetic state of rDNA.
abstract: The synthesis of ribosomal RNA (rRNA) is carefully tuned to match nutritional conditions. In this issue, Murayama et al. (2008) describe a mechanism that couples the energy status of the cell to heterochromatin formation and silencing of rRNA genes. They show that an altered NAD(+)/NADH ratio in response to glucose starvation regulates the silencing activity of eNoSC, a complex consisting of the NAD(+)-dependent histone deacetylase SIRT1, the histone methyltransferase SUV39H1, and a new protein called nucleomethylin (NML). These results suggest a mechanism that links cell physiology to rDNA silencing, which in turn is a prerequisite for nucleolar integrity and cell survival.
authors.affiliation: Department of Molecular Biology of the Cell II, German Cancer Research Center, DKFZ-ZMBH Alliance, Im Neuenheimer Feld 581, 69120 Heidelberg, Germany. i.grummt@dkfz-heidelberg.de
authors.forename: Ingrid
authors.initials: I
authors.lastname: Grummt
authors.forename: Andreas G
authors.initials: AG
authors.lastname: Ladurner
mesh_terms: D000818:Animals; D002466:Cell Nucleolus / Q000378:metabolism; D002470:Cell Survival; D004275:DNA, Ribosomal / Q000235:genetics*; D004734:Energy Metabolism; D044127:Epigenesis, Genetic; D000076983:Histone Methyltransferases; D011495:Histone-Lysine N-Methyltransferase / Q000378:metabolism; D006801:Humans; D009243:NAD / Q000378:metabolism; D011496:Protein Methyltransferases; D037761:Sirtuins / Q000378:metabolism
chemical_list: D004275:DNA, Ribosomal; D009243:NAD; D000076983:Histone Methyltransferases; D011496:Protein Methyltransferases; D011495:Histone-Lysine N-Methyltransferase; D037761:Sirtuins