Regulation of the Activity of Transcription Factors Flashcards
describe transcription factor activity regulation by lipid hormones
lips cells send signals by a lipid soluble hormone
hormones diffuse through cell and bind to a dedicated class of proteins: lipid-hormone receptors/transcription activators
upon binding the hormone-receptor complex moves to the nucleus –> transcription factor, binds to specific response elements in genes to regulate gene expression
what domains do receptors have?
DNA binding
ligand binding
describe the results of the ligand binding experiment
when the ligand binding domain is intact and the cells are treated with dexamethasone, b-galactosidase goes to the nucleus
hormone binding domain is sufficient to translocate the protein to the nucleus
describe the control of RNA pol II pausing
on many genes RNA pol II initiates transcription, then pauses 50-200 bases downstream of the promoter
examples mentioned are regulation of HSF1-regulated genes and the regulation of oncogene MYC
RNA pol elongation is blocked, awaiting a signal by a transcriptional activator
activators stimulate PTEFb
RNA pol II block released
gene is now active
describe activator/repressor binding
bind directly to DNA in promoters or enhancers
affect gene expression by recruiting multi-subunit co-activators/co-repressor complexes that modulate chromatin structure or interact with the mediator and GTFs
activators stimulate the assembly of pre-initiation complexes and move nucleosomes away from the promoters
repressors most frequently work through the build up of repressive chromatin structures
what is chromatin?
DNA in eukaryotes is packaged with nucleosomes
two forms of chromatin:
EUCROMATIN (de-condensed, lightly stained, active)
Heterochromatin (condensed, heavily stained, inaccessible to TFs)
before RNA pol II and GTFs can get acess to promoters, must open condensed chromatin and move away nucleosomes
massive number of factors that work with chromatin to regulate gene expression
what is epigentic regulation?
transcription in eukaryotes takes place on chromatin. chromatin needs to be open for transcription to proceed
what do pioneer TFs do?
establish and maintain open chromatin structure. Do not directly activate transcription
what are the histones and the histone code?
nucleosome is made up of 8 histones: 2 each of H2A, H2B, H3, H4
histones contain core domains that form the highly structured nucleosome
histone N-termini are not structured and protrude away from the histone core. N-termini are modified by post-translational modifications, which dictate the function of the DNA wrapped around the nucleosome
variety of PTMs are referred to as “histone codes”
