Epigenetic mechanisms regulate gene transcription and genomic stability and maintain normal cell growth, development, and differentiation. At the molecular level, epigenetics involves a complex and dynamically reversible set of structural modifications within the nucleic acids and histone proteins that constitute the nucleosome. Epigenetic machinery is composed of three interconnected components working synergistically in the chromatin organization levels, which include DNA methylation, histone post-translational modifications, and regulatory non-coding RNAs (ncRNAs). In the nucleus, chromatin exists in two physical and functional states: heterochromatin and euchromatin. The organizational states of the chromatin are highly regulated by epigenetic mechanisms involving nucleosome, which is the basic packaging unit of chromatin, composed of an octamer of histone proteins (two dimers of H2A-H2B and a tetramer of H3-H4 histones), that constitutes a compact structure with 147 base pairs of DNA turned twice around it. N-terminal tails of histone proteins can acquire post-translational modifications through multiple mechanisms including phosphorylation, ubiquitination, methylation/demethylation, and acetylation, the latter being the most studied. Histone and direct DNA modifications constitute “the epigenetic code”: an interplay between epigenetic factors and positive and negative feedback mechanisms that regulate it. Therefore, understanding the complex interplay of these mechanisms and their role in disease development is essential in the application of epigenetics for drug discovery.
A549 cells treated with chaetocin (a competitive inhibitor for S-adenosylmethionine), or Trichostatin A (HDAC inhibitor). Confocal images (40x) show changes in nuclei stained by Hoechst (blue), mitochondria stained by Mito Tracker (red) and nucleoli and cytoplasmic RNA stained by Syto14 (yellow)
Drug discovery based on epigenetics has seen significant advances in the recent times and epigenetic processes remain an attractive mechanism that could explain the long-term effects of drugs on genomic transcription and health outcomes. A myriad of small molecule inhibitors have progressed to clinical stage investigations to establish convincing benefits in various diseases. Several epigenetic drugs of choice like DNA methyltransferase inhibitors (e.g., 5-azacytidine, 5-aza-2′-deoxycytidine, Trichostatin A), histone deacetylase inhibitors (e.g., vorinostat, romidepsin, belinostat) have been studied widely in several drug discovery projects in academia, biotech and big pharma companies. The potential of epigenetic drugs has been extending to several pathologies, from infectious diseases to
Visikol has developed methods to visualize epigenetic changes at the cellular level, after the drug treatment. Cells treated with different epigenetic drugs are stained with different fluorescent dyes (e.g., stains for plasma membrane, mitochondria, cytoskeleton, Golgi apparatus, lysosomes, nucleus etc.) in live or fixed cells. After labeling different cellular compartments, the cells are imaged on a high content confocal imager. Based on the image analysis, we can quantitively profile multiple phenotypic parameters to better understand the effect of different epigenetic drugs and elucidating their mechanism of action. This approach provides pharmaceutical research support in solving epigenetic drug discovery problems with high specificity and sensitivity with high temporal and spatial resolutions. If you are interested in utilizing this epigenetics approach for your drug discovery projects, please reach out to our team to discuss your project. We are always interested to work together with our clients to develop customized assays to best suit their needs.
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- Frontiers | Epidrug Repurposing: Discovering New Faces of Old Acquaintances in Cancer Therapy | Oncology (frontiersin.org)