Activation and Repression Flashcards
(19 cards)
List the proteins involved in transcription.
Proteins in Transcription
GTFs, RNAP II, Activators, Co-Activators, Repressors, Co-Repressors
What is the function of the co-activator?
Co-Activator
Form molecular bridges between GTFs and RNAP II, remodels chromatin
What is the PPE?
Proximal Promoter Element
Immediately upstream from the core promoter
What is the purpose of the enhancer?
Enhancer
Bind activators
Describe modular enhancers.
Enhancer
Order of binding sites not important, like a pick and mix.
More activators bound = increase in transcriptional activity, like a dimmer switch.
e.g. Hunchback gene promoter and TNF-alpha gene.
Describe non-modular enhancers.
Enhancer
The arrangement of sequences is essential for function, like an on-off switch.
e.g. Interferon-beta enhancer
What triggers TNF-a gene expression?
TNF-a
Viral infection or increased calcium levels
Describe steric hindrance.
Repression
Repressor binding site overlaps the enhancer binding site, which is mutually exclusive thus blocks activator binding as the repressor has a stronger binding affinity.
Describe masking.
Repression
Blocks the activation domain without having to bind to the DNA (some do, some don’t). Changes the activator confirmation, thus repressing transcription.
Describe sequestering.
Repression
Acts in the cytoplasm by binding to ligand binding domains of activators, preventing travel into the nucleus.
Name the subfamilies of chromatin remodelling complexes.
Chromatin Remodelling
SWI/SNF, ISWI, CHD and INO80
Describe histone acetylation.
Histone modification
Lysine residue in the unstructured N-terminal tail becomes acetylated, which reduces the positive charge of the lysine and thus reducing binding affinity to DNA.
Describe epigenetic writers.
Epigenetic proteins
Factors that add histone modifications or deposit histone variants.
May be involved in de novo mods or maintain mods.
Describe epiegentic readers.
Epigenetic proteins
Interpret histone code
Describe epigenetic erasers
Epigenetic proteins
Remove histone mods/variants
What is the polycomb group?
PcG
PcG is a protein involved in gene repressor, they are readers (PRC1) and writers (PRC2)
What is the trithorax protein?
TrxG
TrxG is a protein involved in gene activation. It has reader and writer functions (e.g. Swi/SNF).
Describe non-coding RNAs.
nc-RNAs
Small RNAs regulate gene expression via RNA interference (RNAi).
Long non-coding RNAs recruit histone modelling complexes
Describe the classes of DNA methyltransferases.
DNA methylation
De novo: establish methylation patterns during cell diff, methylate both cytosines on each strand of dsDNA.
Maintenance: Hemi-methylases, maintain DNA methylation patterns after DNA replication.
