Epigenetics: Forgetting Might be as Important as Remembering

Expression of a gene depends as much on its location as its primary DNA sequence. Epigenetic modifications, or the changes to the protein around which DNA is wound, can also alter gene expression patterns. Epigenetic changes can be passed on from parent cell to daughter cell, ensuring each cell line has the proper characteristics consistently over many generations. Transposons or jumping genes are quite distinct from other genes, because they are nearly always epigenetically inactivated. Silencing transposons is important to retain the integrity of the genome, since these mobile genetic elements can insert themselves randomly, causing deleterious mutations and gene silencing.

Scientists have known that once triggered, the maize plant "remembers," and keeps the transposons "silenced" generation after generation, even after the trigger is lost. Researchers at the McGill University and University of California, Berkeley, found that this is not always the case. At certain positions in the genome, the transposon reawakens when the trigger is lost. The discovery suggests that the epigenetic landscape of plant genomes may be more subtle and interesting than previously thought, with the ability to remember epigenetic silencing varying depending on position. Erasure of heritable information might prove to be an important component of the epigenetic machinery.

Read the complete article at http://www.mcgill.ca/newsroom/news/item/?item_id=103077 Download the paper published by PLoS Genetics at http://dx.doi.org/10.1371/journal.pgen.1000216