Active and passive repression
- Created by: natasha8sherry
- Created on: 15-11-13 11:15
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- Transcriptional Repression
- Chromatin + nucleosomes are repressors. Therefore activators are required at all promoters (even in euch areas)
- Relief can come from chromatin remodelling / modifying
- Gene-specific repression is needed to ensure gene is OFF till needs to be transcribed
- E.g. activator A turns on 100 genes, you only want 90 - use repressor to block activation of 10
- Passive repression
- Steric hindrance
- Competitive binding with activator
- Masking / quenching
- Interaction with activation domain
- Interacting with GTF
- Binding to GTF so that activator can't interact with it
- Sequestering activator in cytoplasm
- Isolate activator by repressor holding onto it until signal for release
- Steric hindrance
- Active repression
- HDACs
- E.g. Sin3 + NURD
- Formation of facultative heterochromatin
- Long range repression
- Histone methyltransferases
- Methylated histones can bind silencing proteins
- E.g. HP1
- Directs formation and spread of heterochromatin
- E.g. SUV39H1
- HDACs
- Chromatin + nucleosomes are repressors. Therefore activators are required at all promoters (even in euch areas)
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