M2 L2/3 Flashcards
What is meant by ‘DNA is dynamic’
That DNA can switch between heterochromatin and euchromatin states
heterochromatin
closed, inactive
euchromatin
open, active
What allows DNA to be dynamic
histone tail modifications and NR
Role of PcG
repress transcription
Types of PcG
vPRC1, cPRC1 and PRC2
Role of TrxG
antagonise PcG
Structure of PcG and TrxG proteins
multisubunit complex of proteins. The same core structure interacts with various different proteins to give different functions
PRC1 interacts with — to get cPRC1
CBX
PCR1 interacts with — to get ncPRC1
RYBP
cPRC1 composition and main function
reader domain that binds H3K27me3 (put on by PRC2)
The main role is chromatin compaction
- a positively charged region
- Additional proteins can associate with that help in oligomerisation and protein-protien interactions
Chromatin compaction by cPRC1
+ve charged regions interact with -ve region of DNA between histones, pull histones together
interaction with additional proteins allows oligomerization which pulls nucleosomes and proteins together
ncPRC composition and main function
has enhanced ubq ligase activity - carries out H2A3K119ub
PCR1 core complex
Made up of 2 enzymes that have ubiquitin ligase activity – ubiquitinates H2AK119 (PTM) which inhibits RNAPII
- On its own the PRC1 core complex can’t do much, it needs to interact with other proteins
o With CBX to get cPRC1
o With RYBP to get ncPRC1
PRC2
has HMTase domain that’s catalysed by complexing with other proteins
puts on H3K27me2/3
associated proteins have reader domains that can recognise the marks it puts on and recognise H2AK119ub
