Epigenetics
Three main players
Chromatin
Histone modifications on the nucleosome core particle
Histone modifications determine function
Examples of the “histone code” for H3/H4
Histone tail modifications alter chromatin accessiblity
Histone modifying complexes and nucleosome remodeling complexes recognize the modified histones through specific domains
Is there a histone code?
Spreading of an epigenetic mark and remodelling
Are the histone modifications really epigenetic and thus heritable?
Inheritance of histones after DNA replication
DNA Methylation
Role of methylation in silencing
DNA methylation patterns differ between stem cells and differentiated cells
DNA methylation lies at the heart of Imprinting
RNA meets Chromatin
Short RNAs (21-23 nt) direct silencing of genes in three different ways
Overview
Core features of miRNA and siRNA silencing
Synopsis

Core features of miRNA and siRNA silencing
In general:
– miRNAs- regulators of endogenous genes
– siRNAs- defenders of genome integrity in response to foreign or invasive nucleic acids such as viruses, transposons, and transgenes.
Single-stranded forms of both miRNAs and siRNAs are found to associate with effector assemblies known as RNA-induced silencing complexes (RISCs).