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24 Cards in this Set
- Front
- Back
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What is a transcriptional activator?
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Transcription factors that recruit general transcription factors to individual promoters.
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What is a general transcriptional factor?
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They promote binding of RNA polymerase to the transcriptional start site and mediate the actions of transcriptional activators.
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What is a transcriptional coactivator?
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They stimulate transcription by mediating the binding between activators and general transcription factors by bending DNA or by altering chromatin structure.
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Transcriptional activators have two domains. What are they?
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a DNA binding domain and a transcription activating domain.
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Genetically, how is Beta-thalassemia caused?
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A promoter mutation that causes underexpression of a gene
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Genetically, how is hereditary persistence of fetal hemoglobin caused?
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A promoter mutation that causes inappropriately high gene expression.
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What are the three subgroups of transcription factor?
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Activators
General transcription factors Coactivators |
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What is the duty of the activator?
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To bind to specific upstream DNA sequences and recruit general transcription factors and coactivators.
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What is the duty of General transcription factors?
What is the first of this type to bind to the DNA? |
Assist binding of RNA Polymerase to the transcriptional start site.
TBP (TATA binding protein) |
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What is the duty of coactivators?
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Modulate the activity of transcriptional activators.
Some may assist DNA binding of a General Transcription factor by an activator by bending DNA while others may not bind directly to DNA but act as a bridge between the activator and GTF. |
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Once the GTF is bound to the DNA, this is complete.
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The preinitiation complex
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Once the preinitiation complex is complete, what does it do?
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It recruits RNA Polymerase II to the start site of the gene
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Describe Histone Acetylation/Deacetylation
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Activators recruit co-activators that change chromatin structure by either moving nucleosomes or unwinding DNA around nucleosomes. OR, they can attach small chemical groups to histones.
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What are histone modifying enzymes called?
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Histone acetyl transferases (HAT's)
They attach acetyl groups to histone tails and result in modulation of the transcriptional activity of the promoter. |
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What removes these acetyl groups?
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HDACs (Histone deacetylases) - act as corepressors and lead to repression of transcription by making chromatin more compact.
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What is a constitutive promoter?
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A promoter that is always active and always bound by a transcription factor.
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What is an inducible promoter?
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A promoter that is bound by transcriptional factors and activated in response to cellular factors.
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What is a response element?
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A sequence in the promoter region of inducible promoters that are bound by protein factors only under specific circumstances.
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What is a dimerization domain?
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A functional domain that allows the transcription factor to bind to other proteins to form a homodimer (same protein) or heterodimer (binding to a different protein)
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What is a transcriptional activation domain?
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A portion of the transcription factor that contains amino acids which are responsible for binding RNA polymerase at the promoter
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In a zinc finger, what is the function of each finger?
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The first finger determines the DNA specificity of the receptor
The second finger controls specificity of dimerization |
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What is Beta-Thalassemia?
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A promoter mutation causing an imbalance in the synthesis of alpha and bet chains of hemoglobin. This results in anemia. Beta thalassemia results in impaired synthesis of the beta chain only.
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What is Hereditary persistence of fetal hemoglobin?
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A mutation resulting in increased amounts of fetal hemoglobin.
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What are the two possible mechanisms for this disease?
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1) A point mutation increases the affinity for a transcription factor
2) A point mutation decreases the affinity of a repressor |
