Heritable gene repression through the action of a directed DNA methyltransferase at a chromosomal locus

Smith AE, Hurd PJ, Bannister AJ, Kouzarides T, Ford KG
Source: J Biol Chem
Publication Date: (2008)
Issue: 283(15): 9878-85
Research Area:
Cancer Research/Cell Biology
Cells used in publication:
Species: mouse
Tissue Origin: embryo
Nucleofectorâ„¢ I/II/2b
The ability to exogenously impose targeted epigenetic changes in the genome represents an attractive route for the simulation of genomic de novo epigenetic events characteristic of some diseases and for study of their downstream effects, as well as providing a potential therapeutic approach for the heritable repression of selected genes. Here we demonstrate the ability of zinc-finger peptides to deliver DNA cytosine methylation in vivo to a genomic integrated target promoter, when expressed as fusions with a mutant prokaryotic DNA cytosine methyltransferase enzyme, thus mimicking cellular genomic de novo methylation events and allowing a direct analysis of the mechanics of de novo DNA-methylation mediated gene silencing at a genomic locus, for the first time. We show that targeted methylation leads to gene silencing via initiation of a repressive chromatin signature at the targeted genomic locus. This repression is maintained after loss of targeted methyltransferase enzyme from the cell, confirming epigenetic maintenance purely through the action of cellular enzymes. The inherited DNA methylation pattern is restricted only to targeted sites, suggesting that the establishment of repressive chromatin structure does not drive further de novo DNA methylation in this system. As well as demonstrating the potential of these enzymes as tools for the exogenous, heritable control of cellular gene expression, this work also provides the most definitive confirmation to date for a transcriptionally repressive role for de novo DNA methylation in the cell and lends some weight to the hypothesis that the aberrant methylation associated with certain diseases may well be a cause rather than consequence of transcriptional gene repression.