Sign up for Table of Contents Alerts.
Cell Cycle is published 24 times a year.
Email this page
Print this page
Perspectives
Chromatin Turn Ons and Turn Offs of Ribosomal RNA Genes
Richard J. Lawrence and Craig S. Pikaard
volume 3 | issue 7
july 2004Pages: 880 - 883
We now provide open access to journal articles published online for one year or more. This article may be downloaded at the following link:
Download PDF If the document does not open, please right-click on the link (control-click on a Macintosh) and select the option to save the file to disk.
Eukaryotes have hundreds (sometimes thousands) of ribosomal RNA (rRNA) genes whose transcription by RNA polymerase I helps establish the proliferative ability of cells by dictating the pace of ribosome production and protein synthesis. Interestingly, only a subset of the total rRNA gene pool is active at any one time, making rRNA genes attractive for understanding the dynamic balance between gene silencing and activation. However, the fact that rRNA genes are essentially identical in sequence in a pure species has been an obstacle to telling apart the active and inactive genes. Nature has provided one solution to this conundrum in the form of the epigenetic phenomenon, nucleolar dominance: the transcriptional silencing of one parental set of rRNA genes in a genetic hybrid. Parental genes in hybrids typically differ in sequence as well as expression, allowing a definition of the chromatin modifications of rRNA genes in the on and off states in vivo. By exploiting nucleolar dominance in plants, we recently showed that concerted changes in DNA methylation and histone methylation comprise an epigenetic switch that turns rRNA genes on and off. Independent studies using mouse and human cells have led to similar conclusions, implicating chromatin modifications as important components of the regulatory networks that control the effective dosage of active rRNA genes.
We now provide open access to journal articles published online for one year or more. This article may be downloaded at the following link:
Download PDF If the document does not open, please right-click on the link (control-click on a Macintosh) and select the option to save the file to disk.