Epigenetics

• What is epigenetics?

  The study of inherited variations in phenotypes as the result of alterations in gene expression caused by environmental factors
• What does the epigenome determine?

  Whether a gene is switched on or off
• How does the epigenome work?

  The attachment or removal of chemical groups (epigenetic tags) from DNA or histone proteins
• What does methyl do?

  Clumps histones together
• What does acetyl do?

  Repels histones
• How is cancer caused by epigenetics?

  • Hypermethylation of TSG
  • Hyperacetylation of oncogenes
• What environmental factors impact the epigenome?

  • Pollution
  • Drought
  • Availability of food
• What happens to most epigenetic marks between generations?

  They are removed, but some escape this process and are passed on
• Where does the methyl group attach?

  CpG site- where cytosine and guanine are next to each other
• What affects can hypermethylation have?

  1. Prevents the binding of transcriptional factors
  2. Attracts histones making the DNA inaccessible
• What happens when acetyl is added?

  The chromatin is less condensed, which increases transcription
• What happens when acetyl is removed?

  Chromatin becomes more condensed and transcription decreases
• Which enzyme removes acetyl groups?

  Histone deacetylase
• In which stage are epigenetic tags usually removed?

  Zygote
• Are epigenetic changes permanent?

  No, they are reversible
• How can epigenetics be used to treat disease?

  Act as targets for new drugs- have to be highly specific to prevent damage to other cells
• Which drug can treat methylation?

  Azacytidine
• Where is azacytidine used?

  In chemotherapy for cancers caused by hypermethylation of TSG
• How does azacytidine work?

  Inhibits methylation by physically blocking enzymes
• what drug treats acetylation?

  HDAC inhibitor drugs, romidepsin
• What does romidepsin treat?

  Diseases caused by the decreased acetylation of histones
• How does romidepsin work?

  Inhibits the activity of histone deacetylase