6: Role Of Nuclear Receptors In Cancer Flashcards
(29 cards)
List the modifications of Histone H3 associated with transcriptional activation
- H3-serine 10 phosphorylation
- H3-lysine 9/14 acetylation
- H3-lysine 4/36/79 methylation
- H3-arginine2/17/16 methylation (&H4-arginine 3 methylation)
List some histone 3 & 4 modifications that result in transcriptional repression
- H3&4 lysine deacetylation
- H3 lysine 9 methylation : mediated by G9a & Suv39H, recognised by HP1 associated with repressive complex
- H3 lysine 27 methylation : recognised by polycomb repressive complex
Which repressive complexes are the modifications H3-lysine 9 methylation and H3-lysine 27 methylation recognised by?
- H3-lysine 9 methylation: HP1 (Heterochromatin protein 1)
- H3-lysine 27 methylation: Polycomb repressive complex
What are 4 examples of ATP-dependent nucleosome remodeling complexes?
- SWI/SNF: (switching/sucrose non-fermenting) in yeast
- Brahma: in drosophila
- BRG1/hBrm: Brahma related gene in mammals
4: NURD: (NUcleosome Remodelling and Deacetylation repression complex) contains KDM & HDAC activity
How do ATP-dependent nucleosome remodelling complexes work?
- Utilise the energy released by ATP hydrolysis to reposition nucleosomes along DNA
- Nuclesomal fluidity promotes association of general TFs to promoter region
- Plays a key role ion rendering nucleosomes accessible to HAT-coactivators, the first step in NR-mediated trans activation
T of F:
- ChIP studies revealed that a hBrg1-containing complex was recruited to an Androgen Response Element in ligand-dependent fashion
- SWI/SNF is a nucleosome remodeling complex found in drosophila
- ATP dependent nucleosome remodeling complexes have important roles in the DNA repair response
- F: estrogen response element, not androgen
- F: in yeast, not drosophila
- T
Fill in the blanks:
_____ (SRC-1) was the first identified coactivator (by ____-__-____ analysis) in 1995.
Interacts with PR, ER, ____, ____, ____, ____ via receptor ligands binding domains.
Enhances _____ dependent (AF-2) trans activation by directly recruiting component to of general transcription apparatus and ____/____ and ____.
- NCOA1
- Yeast-2-hybrid
- TR, RXR, GR, PPARs
- Agonist
- P300/CBP and pCAF
What coactivators are amplified in breast cancer, enhancing estrogen-dependent growth stimuli?
NCOA3/SRC-3/AIB1
T or F:
- p160 KAT coactivators vary highly
- there are distinct temporal and spatial expression patterns suggesting limited functional redundancy between SRC1, 2, and 3
- NCoA2 was the first identified coactivator in 1995
- differential levels of p160 CoAct levels modulate NR function in distinct cell type
- F: p160 KAT CoActs are highly similar
- T
- F: NCoA1 (SRC-1) was the first
- T
What are the 3 types of p160 steroid coactivators
- SRC-1: NCoA1
- SRC-2: TIF2/GRIP, NCoA2
- SRC-3: ACTR/AIB1
Describe how knockout mice are used to explore functional redundancy between p160 KAT CoActs?
- NCoA1 -/-: decreased growth of estrogen & androgen responsive tissue, SRC-2 up regulation (compensation mechanism), partial resistance to thyroid hormone
- NCoA3-/-: delayed puberty,decreased productive function, granulosa cells unresponsive to FSH, therefore insufficient estrogen production
- whilst p160 CoActs are similar, we know they are not functionally redundant as knocking out one of them leads to physiological changes
- if they were functionally redundant, they would compensate for one another, and function wouldn’t alter
T or F:
- NCoA1 knock out mice showed lack of response to FSH in ovarian granulosa cells
- The high similarity of p160 CoActs leads to functional redundancy
- Each p160 CoActs exhibit distinct expression patterns
- p160 knock out mice show hormone-resistant phenotypes
- F: this is NCoA3
- F: there is some functional redundancy, but each CoAct plays a unique role
- T
- T
Describe how LxxLL motifs have preferences for each p1660 CoAct.
The number of and spacing between each LxxLL motif underlies preferences for each p160 CoAct
Using p300 and SRC-3 as an example, describe how CoAct modifications can be exploited
p300-mediated acetylation of lysine residues adajacent to the NCoA3(SRC-3) NR box causes NcoA3 to dissociate from liganded ERa
This terminates transcriptional activation
Using p300 and NCoA3 as an example, describe how modulation of CoA activity enables integration of multiple signal pathways
Phosphorylation of NCoA3 (SRC-3) by MAPK increases the half-life of its association with p300
Directly influences the transcriptional response to specific endocrine signals
What traits are observed in NCoA-/- p160 knock-out mice?
- Subtle hormone resistant phenotypes
- Exhibit decreased growth of estrogen & androgen responsive tissues
- SRC-2 (TIF2) is upregulated as a compensatory mechanisms
- partial resistance to thyroid hormone
What sequence is critical for interaction of p160 CoACt with NRs?
Leu-x-x-Leu-Leu sequences in NR-boxes (LxxLL motif)
How do these effect NCoA3:
1. P300-mediated acetylation
2. Phosphorylation by MAPK
- Causes CoAct to dissociate from liganded ERa
- Increases half-life of its association with p300
Mutations in what protein are association with Rubinstein-Taybi syndrome?
CBP
What does CBP stand for
CREB (cAMP response element binding protein) binding protein
T or F:
1. p300/CBP diminish transactivation of multiple, distinct classes of TFs
2. Mouse KOs indicate there is limited functional redundancy between p300 and CBP despite high homology
3. Mutations in p300 are associated with Rubinstein-Taybi syndrome
4. P300/CBP can acetylate non-histone targets
- F, they enhance transactivation
- T
- F, it is CBP not p300
- T, for example, SRC-3
What gene is NCoA2 known to fuse with in acute myeloid leukemia?
KAT6A (MOZ), a histone acetyltransferase
What is the function of the mediator complex and what is another name for it?
- recruits RNA poly II holoenzyme to the promoter
- DRIP/TRAP complex
Which histone lysine methylation is associated with gene repression?
H3K9 and H3K27
