#27 Gene Regulation 2 Flashcards
Difference between bacterialand eukaryotic gene expression
- Bacteria have one polymerase.sigma fctor guding to its promotor site while Pol II has amny polymerases
2, Eukayrotes lack operons. Each gene is sepearately regulated
- instead of small number of repressors and activators per gene in bacteira, euk genes are controlled by alarge nubmer of TF, soemtiems hundreds, many facotrs at at long distances
- Mediator
- DnNA is packed into chromatin to provide more opporutnies for reuglatino
What is Mediator?
central component of eukarytoic gene regulation , 24 subunit complex’ mediates communication between regulatory transcriton factors and Pol II
What are tewo modular designs of gene activator proteins
- dedicated to site-specific DNA recognition (DNA-binding domai)
- activation domain, initaites transcirtion by recruiting, oreitning and or modifying generatl TFs, Mediator and/or Pol II
One activator in euk can turn oN many genes
yup
What is transcriptional synergy
when activotrs bind simulatneously the affet is multiplicative
what are insulatros
activator preotins can act on genes a great distane away form teh enhancer binding site. This distance might be problematic b/c one activator preotine might upregualte the tx of too many gees
What are 4 ways that eukaryotic ACTIVATOR proteins can alter loacl structure of hromatin to enchance initiation of Tx
- ATP dependent chormatin remodeling complex decondeses the chormatin structure to make DNA more accesible
- histone chaperones remove some histoens tomake DNA more accessible
- modified histones are swapped for nmodified ones to alter the “histone code”
- Histone acetyltransfreases (HATs) acetylate histone tail proteins to alter the “histone code”
N terminal tails of histone sare accessile an reversibly modifed to regulate gene expression by activating or repressing Tx
yep
What are HATs (histone acetyltransferases)
they acetylate histone lysine residues
acetylation by HATs repalces positive amin gorup of LYSIN side chain with NETURAL acetyl group to reduce the positive charge of hisone particels
less positive cahrge weakens ability of histones to bend DNA–> chromatin opes up and TRANSCRIPTION IS ACTIVATED
what does acetyl to do histone
is neutralizes posiive charge to ACTIVATE trx
what are HDACs (histone dacetylases)
remove netural acetyl group form modified lysin residues, leaving bahind a positively charged amine
dacetylation by HDACs increase the positive charge of histones to help neutralize the negative chare of DNA, thereby promoting DNA benind and wrpping
TX is REPRESSED
does DHACs activate or rperess transctipion?
Repress!
what happens when ther eis an imbalance of acetylation and deacytlation of hisone lyine
luekemia, epithelial cancer, fragile X syndeom ,Rbuinstein Tyabi sydro e
what are two toher reversible modifeicaiton
Ser/Tyr phosphyrtlin and dephosphyorylation as well as Lys methyaltino adn demethylation
What are 6 ways to repress eukaryotic gene transcription
- competitve DNA binding
- masing the activation surface (repressor binds to sbidn site as well as activator)
- direct interaction of repressor with TF
- recrutiement of chromatin remodeling complexes
- recruitment of hisotne dacetyalses
- recrutiemten of histone methyl transferases
what will happen if repressor protein recruites hisont deactylases
represses transcritpion
what happens when hisont methytransfeases recruites
recruits proteins that maintin chromatin in a trascriptionally silent form
Lysing and arg residues are methylated
what amino acids are methylates on histones
Lys and Arg
Diff between HLH homodimer and heterodimer? which one is active?
Homodimer- 2 intact proteins and ACTIVE
heterodimer- one shorter b/c DA recognition helix was delted
what is Ey
master regulator
what is NF-kb
regualtes >400 genes
linked with inflammatory diseases, cacer, pumonary, autoimmune, skin ,enruodegeneative CV,
what is epigenetics?
affects phenotype without changing genotype
what are 4 different epigenetic modifiecations?
- protein A is a regulator portien taht actiates its own expression
- Methylation of DNA is maintatined after DNA replication (so trais CAN be inherited)
- chroamtin has its histones methylated –> pretins that recognize histone code help keep it transcriptiaonlly SILENT
these sites of odification rerut reaer write complees that resore local hormatin reigon to sam leel of modifiaction that was fodn in parent chormatin region
- Aggregated proteins have two fomers
fucntional form and aggreated form which causes disease–> aggregated forms polymer and can be inherited
what dos DNA methylation do to transcription
it represses transcritpion
silecne a gene or region of chromatin
doesnt affect geomtry of CG pair
accessible for preotien recognition but doenst interfere with base pair fomration
