Histone modifications
- Created by: Ellie0o0o
- Created on: 27-04-15 16:41
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- Histone Modifications
- Covalent histone modifications
- Phosphorylation
- Acetylation
- Lysine residues
- Free amino group replaced by acyl group
- Histone becomes netutral
- Enhances transcription
- Lysine residues
- Methylation
- Most common is 5 methyl-cytosine
- 5-azacytiolone is an analogous base which cannot be methylated. When added, silent genes become active
- Mono- di- or tri- methylation
- Tri- gene silencing
- Mono- active enhancer
- Ubiquitination
- Histone Variants
- H2A and H3 variants found in DNA
- Low frequency
- Have minor differences in amino acid sequences
- E.g. Histone 3.3 added in transcription coupled process. Helps maintain gene activity
- H2A and H3 variants found in DNA
- Proteins associate
- Writers
- Acetyltransferase
- Readers
- Bromodomain proteins
- TFIID
- Bromodomain proteins
- Erasers
- deacetylases
- Writers
- Histones have...
- N-terminal unstructured tail
- Extends out from the core
- Subject to covalent modification
- Flexible due to lack of structure
- C-terminal histone fold
- Allows histone dimerization
- Highly structured
- N-terminal unstructured tail
- Remodelling falls into 2 types
- Histone Modifying Complexes
- HATs
- Histone Acetyl Transferases
- Acetylation
- Lysine residues
- Free amino group replaced by acyl group
- Histone becomes netutral
- Enhances transcription
- Lysine residues
- Acetylation
- e.g. GCN5
- Histone Acetyl Transferases
- HDAC
- Histone deacetylases
- Repress transcription
- Histone deacetylases
- HATs
- ATP-dependent remodelling
- Varies hugely
- Several complexes use ATP hydrolysis
- Large with common subunits
- Fall into 3 groups by ATPase domain
- Histone Modifying Complexes
- Removed for replication, so replication is a "window of opportunity" for change
- Covalent histone modifications
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