Epigenetics
Control
Treated
Lyse in Polysome Lysis Buffer
Immunoprecipitate with antibody to
protein of interest with protein A/G magnetic beads
Immobilize magnetic bead bound complexes with magnet and wash off unbound material
Ageing can be thought of as how many times our stem cells have had to divide. In older individuals, there is an accumulation of these epigenetic events that is easily measurable in DNA. Every time a stem cell divides for either normal homeostasis or to repair an injury, it ages a little more with a decline in function. Stem cell ageing explains why adults who have been exposed to sun damage, for example, have skin that appears older than similar aged adults who have had minimal exposure to the sun. Every time the skin peels, the damage needs to be repaired by stem cells, which must divide. And every time a stem cell divides there is a finite chance of some sort of epigenetic alteration. Unlike acquired DNA mutations, epigenomic changes are reversible. If they were permanent, ESCs would never be able to differentiate into spe- cialised cells crucial for normal human function- ing. Given the influence of extrinsic environmental factors on the epigenome and the reversibility of these modifications, it is possible that ageing can be modified at the epigenetic level. In fact, sirtuins, a class of proteins that possess histone deacetylase activity, have been under intense investigation since the discovery that they can extend the lifespan of yeast, worms and flies. The role of sirtuins in pro- moting human longevity and avoiding or delaying the onset of age-associated disorders is currently under investigation.
Targeting the epigenome Extract RNAs
Detect by qRT-PCR, RNase Protection,
Microarray, Sequencing
Dysregulated epigenetic modifications are now believed to play important roles in the onset and progression of human diseases, and it has been sug- gested that epigenetic changes may give rise to dis- ease much more frequently than genetic variants19. In fact, a number of diseases and developmental disorders have been found to involve, and possibly be caused by, epigenetic alterations, including Beckwith-Wiedemann, Angelman, Prader-Willi, and Silver-Russell syndromes, Type I and Type II diabetes, autism, neurological disorders, obesity, almost all cancers and even cocaine addiction. From a drug discovery perspective, the fact that the epigenome is dynamic and the modifications reversible, targeting the epigenome to change the patterns of gene expression in an attempt to cure disease is a very real possibility.
Protein of interest Other proteins RNAs
Antibody Magnetic Bead Magnet
Figure 6: RNA-binding protein immunoprecipitation 34
A number of epigenetic drugs have already reached the market. Two DNA hypomethylation agents, Vidaza (azacitidine) and Dacogen (decitabine), are FDA-approved for the treatment of myelodysplastic syndromes (MDS), characterised by frequent epigenetic abnormalities and rapid evolu- tion into acute myeloid leukaemia. Two histone
Drug Discovery World Fall 2011
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