Transcription and replication result in distinct epigenetic marks following repression of early gene expression
DNA in higher organisms is packaged by proteins known as histones. In response to external factors, the histones can be tagged at precise locations by addition of methyl groups that are read to regulate the expression of genes associated with the DNA. It has been thought that when a cell divides, the location of the methyl groups in these histones is duplicated along with the DNA.
Recent work from Barry Milavetz’s laboratory group at the University of North Dakota now suggests that this may not always be the case. In the histones of simian virus 40, which are very similar to cellular histones, when the DNA is duplicated methyl groups may be introduced at new sites in response to external factors. In other words, an external factor can dictate the precise location of the tags based on whether the gene is being expressed or duplicated. Therefore, the duplication of DNA may serve to allow switching of the location of methyl groups with a subsequent change in the potential expression of the genes in the DNA associated with the newly modified histones.
This result may help to explain why there are so many forms of histone methylation. The introduction of methyl groups when DNA is duplicated may play an important role during development, say the authors.
“Transcription and Replication Result in Distinct Epigenetic Marks Following Repression of Early Gene Expression“, Les Kallestad, Emily Woods, Kendra Christensen, Amanda Gefroh, Lata Balakrishnan and Barry Milavetz, Front. Genet. 4:140. DOI: 10.3389/fgene.2013.00140
Frontiers in Genetics