Term
What is deleting mapping and what was the result of this for the PEPCK gene? |
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Definition
Deletion mapping to find regulatory sequences (positive and negative!): The experiment looked at the proximal promotor elements in the PEPCK gene and effect of deletions in the promotor region (black bars).
A normal promoter with the CAAT, GC and TATA box had 100% activity. When certain elements in the proximal area were deleted, the promoter activity decreased with variations depending on the site. TATA box dropped to 38%, GC box dropped to 14% and CAAT Box to 50%. All these indicated the importance of those specific regions. One region dropped to 95% and indicated that it is probably not that important.
NOTE: In the distal promoter element region, removal of that region, gave promoter activity of 114%. This probably means that this region is changing the expression of gene involved in binding of a repressor
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Term
What is needed for RNA Polymerase II binding to a promotor?
Slide 33 |
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Definition
1. Basal TFs at every Pol II promoter
2. DNA-binding transactivators which bind to enhancers and facilitate transcription
3. Coactivators - these act indirectly for RNA poly II. These mediate the relationship between the transactivators and the Poly II complex.
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Term
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Definition
TATA binding proteins (TBPs)
A
B
D
E
F
H
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Term
What are DNA-binding transactivators and what do they do?
What are these sensitive to?
What are the levels of specificity? |
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Definition
Act as protein dimers on the DNA- these have DNA binding domains
Bind to enhancers or upstream activator sequences to faciliate transcription.
Some are sensitive to binding of signal molecules
Some are specific for promoters
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Term
| What role do Coactivators play when RNA Pol II binds to the promoter? |
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Definition
They act indirectly
Bridge between DNA-binding transactivators and complex composed of Pol II and the general (or basal) transcription factors.
There are two which are important.
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Term
What are the two classes of Coactivators for RNA Pol II binding?
What do each of these do? |
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Definition
TFIID coactivator activity is needed for many genes (is complexed with TBP and TAFs)
Mediator coactivator is required for both basal and regulated transcription at promotors used by RNA Pol II. Binds to the C-terminus of the large subunit of RNA Pol II and stimulates phosphorylation of that region by TFIIH
NOTE: Another class is involved in chromatin remodelling
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Term
What is the function of Steriod hormones in relation to DNA?
How do these hormones enter the cell?
What happens when the hormone binds to the receptor? |
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Definition
Gene activation/ DNA transcription
Diffusion
The binding causes the receptor to translocate to the nucleus
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Term
In gene activation by steriod hormones, what happens when the receptor reaches inside the nucleus?
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Definition
•In the nucleus the receptor acts as a transcription factor and binds to the hormone response element of the DNA.
Here the receptor then becomes a DNA-binding transactivator
•Binding of two adjacent receptor molecules leads to formation of a dimer, which activates transcription
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Term
How many nuclear hormone receptors are there in the human genome?
What is their function?
What is the structure and the purposes of these structures? |
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Definition
About 50
Mediate the effect of steroid, thyroid and retinoid acid hormones and facilitates DNA transcription
The nuclear hormone receptors have 2 conserved domains:
DNA binding domain (2 zinc fingers) and a ligand binding domain
DNA binding sites are called hormone responsive elements (HREs)
The nuclear receptors need the ligand binding domain for when they bind to the hormone in the cytoplasm
The DNA binding site or domain is needed when the receptors take on the function of the DNA-binding transactivator.
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