SKAFAR4 Nuclear Receptor

nibbs06's version from 2016-04-16 22:37


Question Answer
What do nuclear receptors mediate and where are they involved? Steroid and thyroid hormones & Breast and prostate cancer and treatment
What are nuclear receptors referred to as? Ligand modulated transcription factors
How were target tissues demonstrated in regard to ligand modulated TF’s?Estrogen injected in rats bound to estradiol in target tissues (uterus) vs. binding to non target tissues (lungs)
Why is the ecdysone receptor in Drosophila relevant to transcription? Where is it most prevalent?It is a protein that termed the receptor association with transcription & Bands of chromosomes (site of uridine)
Why was the mouse model relevant when observing TFM (testicular feminization)? What was discovered from this?Mutated mice (clustering DNA and androgen binding proteins) lacked the androgen receptor – which would show that they are ligand modulated transcription factors & Coactivation – proteins that interact with nuclear receptors activate transcription
What are the 2 criteria that the superfamily nuclear receptors have when sharing a common domain? Dimers & DNA sequence
Why is Drosophila useful in replication studies?Their salivary gland replicates by 1000 fold and it remains in the strands
What does chromosome puffing refer to?Bands and interbands changing during development
How is the DNA sequence different in steroid receptors, dimeric orphan receptors, heterodimers, and monomeric orphan receptors, respectively? Steroid – short indirect DNA sequences Dimeric - short direct DNA sequences, Heterodimers – short direct DNA sequences & Monomers – single DNA repeat
What are the 3 methods of Estrogen binding?Classical – Ligand binds, moves to nucleus, binds to receptor, dimerization, ERE, chromatin remodeling, transcription, Ligand-independent – active receptor on membrane, phosphorylation of receptor, bind to ERE, protein synthesized & ERE-independent – E2 binds to receptor, no ERE binding, interacts with other proteins instead (Fos and Jun) (PROTEIN-PROTEIN MEDIATED)
Why is SRC referred to as a platform protein during the activation state? What enzymes are activated? It binds to its receptor and recruits other proteins to build a transcription initiation complex Histone acetyl transferases via CBP/p300
What is an example of a selective receptor mediator (SRM)? Why is it unique? Tamoxifen Agonist in uterus and antagonist in breasts (used to treat breast cancer)
What balances must we consider in changes made on nuclear receptor activity? Cell signaling (acetylation, phosphorylation, ubiquitination) Interactions between co-activators and co-repressors.
Where is a phosphorylation site missing on the estrogen receptor? Beta receptor – specifically in the DBD (DNA binding domain)
Which phosphorylation sites are stimulated by estrogen? Growth factors? Estrogens – CDK (S104), TFIIHCDK (S118) & Growth factors – MAP (S118), RSK (S167), PKA (S236)
Extracellular signaling affecting tyrosine kinase receptors are activated and undergo, Ras-raf-mek-MAPK to strongly stimulate phosphorylation on ER. It may also initiate PI3k, PIP, AKT to phosphorylate on ER. What are the chromatin dynamics on estrogen receptor at the pS2 promoter when estrogen is not present? Proteins are constantly binding and dissociating from the chromatin. No RNA pol, no histone modification, no histone acetylation. Receptor binds and dissociates constantly in all cycles – cannot retain co-activators without estradiol. All cycles are unproductive – TATA remains but no transcription = HDAC takes nucleosomes to ground state.
What are the chromatin dynamics on estrogen receptor at the pS2 promoter when estrogen is present? Proteins are constantly binding and dissociating from the chromatin. RNA polymerase, histone modification and acetylation Receptor binds and dissociates only in cycle 1 – which is unproductive. Cycle 2-5 = receptor binds and recruits RNA pol = transcription occurs – HAT modifies – TATA is activated – co activators are present. HDAC always restarts the process Brg and Brm are present.
What does tamoxifen act on and what change does it cause? Does protein displacement disrupt the structure? ER alpha – disrupts interactions between the leucines (LXXL) by blocking co-activators & Yes, it disrupts the structure.
What are zinc ions responsible for when interacting with DNA binding domain? Properly folding proteins
What is the driving force between protein and DNA interaction? Hydrogen bonding
What type of protein is GPR30? Membrane bound estrogen receptor
How do we show we have a receptor? By allowing it to bind to a receptor – forming a saturating curve
What are differences between GPR30 and nuclear receptors?GPR30 Scatchard plot is linear. On and off rate is very fast (when receptor comes on and off) & On is fast in nuclear but off is slow Very specific for E2 binding