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15 Cards in this Set
- Front
- Back
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what TF's can act as activators by acting as anti-repressors of histones? how do they work? |
GAL4 and sp1, they force nucleosomes outside of the promoter region |
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what is an example of a DNA NUCLEOSOME-FREEZONES? |
SV40 |
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what do DNase 1 hypersensitive regions show? |
Chromatin exposed by transcription or structural changes is susceptibleto digestion by low DNase I concentration (active-gene, nucleosome free-areas digested, and smaller fragments) |
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what does acetylation or phosphorylation of a histone tail do? (2 things) |
acetylation/phosphorylation targets lysines and neutralizes its positive charge, thus reducing its affinity for the negatively charged backbone of DNA also creates binding sites for chromatin-modifying enzymes (and reduces the ability for nucleosomes to condense) |
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what does HAT, HDAc, HMT, HDM mean? what are they referring to? |
HAT: histone acetyl transferase HDAc: histone deacetylase HMT: histone methyltransferase HDM: histone demethylase refers to structure of histone tail modifications |
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what allows proteins involved in transcription to bind to acetylated histones? what about methylated histones? |
bromodomains chromodomains |
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histone acetylation looses what? what does this do? |
it looses bound DNA in nucleosomes which allows for gene activation by reating a transcription permissive environment |
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whats the main difference between acetylation and methylation in terms of turning on and off transcription? |
methylation is associated with transcriptional repression, acetylation is activation |
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what does histone deacetylase do? |
tightens DNA binding in nucleosomes thus gene repression |
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what is chromatins response to presence and absence of a thyroid hormone? |
repressed chromatin when no thyroid hormone, active chromatin when present
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how do we know that a physical association exists among TF's, co-repressors and HDac's? |
by epitote tagging one of the components and immunoprecipitating the whole complex w/ an antibody against the tag |
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describe TF Mad-Max |
works as an activator or repressor depending on its partner in a heterodimer: if myc bound = activator, if mad1 bound = repressor |
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what is the mammalian Sin3 co-repressor called? |
SIN3A |
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what are the four classes that alter the structure of the nucleosome cores to make DNA more accessible? what do they all have in common? |
1. SWI/SNF Family (switch sniff) 2. ISWI (imitation switch) family 3. NuRD 4.INO80 an ATPase component |
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describe human IFN-Beta promoter modification and remodelling |
activations recruit GCN5 (a HAT) which acetylates lysines on H4 and H3 enhancer complex recruits a kinase that phosphorylations H3, which allows GCN5 to acetylate H3 further acetylation of lysine of H4 attracts nucleosome remodeling complex (SWI/SNIF) this complex permits binding of TFIID, TFIID moves nucleosome downstream so transcription can become |
