Dr. Kaushik Ragunathan publishes in Science Magazine
Our bodies consist of millions of genetically identical cells which display distinct phenotypic states. A major mechanism by which eukaryotic cells regulate how genes are expressed involves post translational modifications of DNA packaging proteins called histones. Although unique patterns of histone modifications are known to be associated with distinct gene expression states, it remains unclear as to whether the modified histones themselves are sufficient to act as the determinants of epigenetic memory. In a recent study published in Science, Ragunathan et al. show that a histone modification that is conserved from humans to yeast (methylation of histone H3, lysine 9) and is associated with silencing gene expression can be inherited in the absence of sequence-dependent initiation signals. The stability of the epigenetic state is determined by the activity of enzymes that promote turnover of the histone mark, histone exchange associated with transcription and dilution of histones during DNA replication. Using yeast as a model organism, the study showed that a memory of the silent epigenetic state can in principle persist for over a hundred cell divisions after removal of the initial stimulus.
Dr. Kaushik Ragunathan received his doctorate from the University of Illinois in biophysics in 2012. His research was conducted under the tutelage of Dr. Taekjip Ha.