Theory of Epigenetic an der RWTH Aachen

1. DNA methylation
2. histone modifications
3. ncRNAs (noncoding RNAs)

1. DNMTs (DNA-Methyltransferase)

Is also associated with gene repression but can have more functions

• Chromatin condensation is dependent on histone modifications
• Associated with gene repression (no binding of transcription factors), how tight or lose the chromatin is wrapped

• affect gene translation and transcription
• more noncoding regions than coding regions in the DNA 
• regarded as critical regulators of gene expression

• Self-sustaining loops (involving DNA): autoregulation of gene activity via their protein products
• structural inheritance (not involving genomic DNA): the transmission of cell structures from cell to cell (i.e. membranes, mitochondria), or organism to organism (i.e. prions, cilia, egg factors). 

• defined as transmission between generations, but not involving direct exposure
  • involves a germ line transmission between generations without direct exposure to the environmental factor
• Maternal transgenerational effects:
  • Phenotype in F3
• Paternal transgenerational effects 
  • Phenotype in F2

• Chromosomes: only visible during mitosis in its very condensed form
• DNA + Proteins (mainly histones) = Chromatin
• Typical eukaryotic cells: 2m DNA packed into 10 μm nucleus (diameter) in neurons
• Huge capacity which has to happen very coordinated > when to pack/ unpack 
• Chromatin structure is dynamic

• are the major protein complexes of chromatin
• Small (100-140 aa) and positively charged > DNA is negatively charged

146 bp

• reach out of the nucleosome and are mostly subject to posttranslational modifications like acetylation, methylation, phosphorylation, ubiquitination etc.

• Canonical histones are replaced by histone variants
• Histone tails are modified
• The histone octamer is moved to a new position along the DNA 
• Can have different effects on gene expression

• Not genes are changed -> readability is changed 
• Definition: Change in the readability of our genes without changing the sequence
• Still no clear definition