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35 Cards in this Set

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model of tfiiia bound to dna of the 5s rRna
Zn fingers containing TF .. enhancing binding by interacting simultaneously with the DNA
example of zn finger
contains TF= GATA used for cardiac m. development
HMG-box
High motility group
three alpha helical regions
dna bending
ex. of HMG-box
SRY gene
UBF
mutliple HMG boxes
bends DNA stongly in dimeric form
Leucine Zipper
leucine rich regions in two proteins to form the dimer
-adjacent to the zipper region is basic aa segment- bZIP
ex. Fos and Jun
Helix-loop-helix
protein dimer formation-50aa
basic aa (bHLH)
ex. MyoD-muscle differentiation
Nuclear Hormone Receptors
mediate the effect of steroid, thyroid, and retinoid acid hormones
-2 conserved regions
DNA binding domain
Lingand binding domain
-
Hormone responsive element
DNA binding sites
2- 6 nucleoide repeats
What are needed for nuclear hormone receptor mediated gene expression?
coactivators
Explain Estrogen coactivator story
Folding of the estrogen receptor is dramatically changed upon binding of estrogen.
No effect on the affinity of the receptor response elements in the DNA
-immediate effect of estrogen binding is exposure of abinding site for the co-activator
Tamoxifen
Estrogen analog
-distorts the structure of the receptor and blocks the binding of the coactivator to the estrogen receptor
Where does HAT transfer acetyl groups?
transfers acetyl group from acetyl Coenzyme A to Lys and Arg residues in Histones amino termianl groups
What is the effect of acetyalation of histone tails at a larger scale?
Prevents chromatin from folding in compact structures--euchromatic state
What are the effects of acetylation of histone tails at a finer scale?
Incrases access of specific DNA regions to ineracting proteins-promotes Transcriptional activation
What do co-repressors do?
They lead to transcriptional repression in conjuction with nuclear hormone receptor
What are examples of co-repressors
SMRT
N-Cor
Int he absence of ligand, what does the corepessor do? presence of ligand?
-ligand binding domain binds to corepressor
-repressor is released when ligan is present
HDAC are associated with what?
Transcriptional repression
Explain the epinephrine example:
-Epi activated G-protein receptor
-activated g-protein binds and activated adenylyl cyclase--inc. cAMP levels
-cAMP beinds to PKA
-PKA phosphorylated CREB
-p-CREB binds the coactivator CBP which leads to histone acetyalation and chromatin remodelling facilitating transcription
When is the LDL receptor regulated? at low or high cellular cholesterol.
LDL receptor is regulated with cellular cholesterol is low
What is the actual cholesterol sensor?
SCAP
SCAP mediates the release of what protein into the nucleus
SREBP
What does SREBP do?
Binds to the sterol responsive element in the LDL receptor and recruits a histone acetyl transferase and together with the TF the RNA Pol II is puased into action
Methylation in euk. DNA is limited to?
cytosine bases in CpG dinucleotides
Where are unmethylated CpG found more frequently?
Gene promotor regions where they are protected from metyhlation and deamination
Transcriptionally active chromatin:
Chromatin structure: open-euchromatin
DNA methylation: unmethylated
Histone acetylation: acetylated
Transcriptionally inactive chromatin:
Cromatin structure: heterchromatin-
condensed
DNA methylation: methylated
Histone acetylation: deacetylated
Where is the Prioximal promoter elements located
100-150bp of transcrption initiation side
What does the Core promotor site consist of?
From TATA box to transcription inititation site.
CAAT box is the binding site for
CTF1
GC box is the binding site for
GC
Examples of distal promoter elements:
IRE,CRE-1, TRE,GRE
Enhancers do what:
Make contact with theinitator site through transactivatros
Insulators do what:
Limit the action range of enhancers