Epigenetics
E
pigenetic mechanisms are inheritable fac- tors that regulate genetic expression with- out changing the DNA sequence1. These factors are observable as DNA methylation, his- tone modification and small regulatory RNAs. In recent years the field of epigenetics has grown into one of the most dynamic areas of biological research, and is increasingly the focus of drug screening activities. Histones, the protein compo- nents of chromatin around which DNA can wind for compaction and gene regulation, play a key role in epigenetics. Histone modification occurs when the binding of epigenetic factors to histone ‘tails’ alters the extent to which DNA is wrapped around histones and the availability of genes in the DNA to be activated. Some of the epigenetic factors that bind to histones include methyl, acetyl, phosphate groups and ubiquitin and sumo proteins. All of these factors and processes can have an effect on health, possibly resulting in can- cer, autoimmune disease, mental disorders, or dia- betes among other illnesses.
The epigenetics research field has been mainly dominated by DNA methylation studies after bisulfite treatment (this provides complete cyto- sine to uracil conversion in DNA for rapid and precise methylation detection by a host of down- stream procedures) and chromatin immunoprecip- itation (so-called ChIP, a method used to deter- mine the location of DNA binding sites on the genome for a particular protein of interest). However, realisation that the key epigenetic enzymes classes/proteins themselves represent important therapeutic targets has prompted the development of a range of biochemical enzyme assays that are directly amenable to screening and the investigation of cellular epigenetic modifica- tion assays.
Alerted by a recent SBS session devoted to epige-
netics2 and in response to growing vendor interest in this area, HTStec undertook a survey in June 2010 to document current practices and prefer- ences in epigenetic enzyme screening assays, and to understand future user requirements3. In this arti- cle we discuss some of the survey findings and review details of how vendors are starting to address the needs of the screening community.
Current perception of epigenetic screening
The current perception of epigenetic screening by the majority (52%) of survey respondents was ‘one of today’s most exciting biological target areas, somewhat comparable to kinase situation, just time is needed to develop’, this was followed by ‘it
Drug Discovery World Spring 2011
Figure 2: Current perception of epigenetic screening
One of today’s most exciting biological target areas, somewhat comparable to kinase situation, just time is needed to develop
It will remain challenging until the biology and screening tools catch up with the hype
The lack of follow-up biology will create a significant obstacle for the foreseeable future
It will never be like the kinase situation as the assays and methodologies are too diverse
No point in screening or profiling targets that have unknown disease relevance
4% 4% 0% © HTStec 2011
0% 10% 20% 30% 40% 50% 60% % Responding
41% 51%
Figure 3: Therapeutic/disease areas targeting/using epigenetic enzyme assays
Inflammatory disease/Autoimmune CNS/Neurodegeneration/Pain Metabolic disease/Diabetes Oncology
Anti-infectives/Anti-viral Cardiovascular
Other 16% 15%
0% 10% 20% 30% 40% 50% 60% 70% 80% % Responding
© HTStec 2011 71% 38%
29% 29%
28%
Figure 4: Key epigenetic enzyme classes/proteins of greatest interest
Deacetylation – histone deacetylases (HDAC & Sirtuins)
Histone Methylation – histone methyltransferases (HKMT & HRMT)
DNA Methylation – DNA methyltransferases (DNMT) Demethylation – histone demethylases (HDM)
Ubiquitination – ubiquitin ligases (E1, E2, and E3) Acetylation – histone acetyl transferases (HAT)
Binding Proteins (eg Bromo, Chromo and Tudor Domains etc)
Dephosphorylation – phosphatases in relation to histones Phosphorylation – kinases in relation to histones Deubiquitination – deubiquitinases (DUB) Sumoylation – SUMO ligases
4.98
4.61 4.72 4.74
1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 © HTStec 2011 10.00 11.00 RANKED ORDER of interest, where 1 = least or no interest and 11 = greatest interest 7.33
6.85 6.89
5.85 5.51 8.11 7.86
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