Leff9 Transcriptional Regulation and Epigenetics

nibbs06's version from 2016-04-16 23:47


Question Answer
What does PEPCK get turned on by? & Turned off by? Glucagon turns it on. Insulin turns it off
Draw the pathway of glycolysis and gluconeogenesis (slide 9)Did I tell you that you look pretty today?
True or False. Hormone signaling that affects enzymatic activity responds to changes in the quantity of enzymes. False, change in activity.
What is the main enzyme that carries out the step from oxaloacetate to phosphenolpyruvate and is known as the committed step for gluconeogenesis (most carefully regulated step)? Phosphenylpyruvate Carboxykinase (PEPCK)
Glycolysis is regulated at the level of ______ _______, while gluconeogenesis is regulated at the level of _______ __________. Enzymatic activity (controls activity of enzyme). Gene transcription (controls how much of the enzyme)
Increasing PEPCK would ________ gluconeogenesis (increase/decrease).Increase
What is the main enzyme that carries out transcription? RNA polymerase
What is the difference between transcription factors and transcriptional co-factors? Transcription factor – sequence specific DNA binding protein that regulates transcription of more than one gene Transcription co-factor – do not directly bind to DNA – bind to transcription factors
Where is the orientation point of most genes? Nucleotide at the beginning (+1 or 5’ UTR site)
When referring to the PEPCK regulatory gene, what transcriptional co-factors (activator) are present? PGC1a & CBP
What are the 3 transcription factors that regulate PEPCK gene transcription? CREB – increased by glucagon, Foxo1 – inhibited by insulin. And HNF4 – increased by glucagon
What disease is PEPCK overexpressed in? Diabetes
What receptor signaling is activated when glucagon induces CREB? What does this lead to? GPRC (s). It leads to CREB phosphorylation and activation of a transcriptional co-activator CBP – activates gene further.
What regulates and ultimately deactivates CREB to remove the phosphate after it has been initiated by glucagon and activated by phosphorylation? PP-1.
What does CREB stand for? CyclicAMP Response Element Binding Protein
What is the classic transcription factor and transcription co-activator interacting compounds that increase transcriptional activity? HNF4 and PGC1
Increase in cAMP will lead to an increase in: What typically increases levels of cAMP? PEPCK, PGC-1 & Glucagon (during fasted state)
What happened when mice were refed after a fasted state? The PGC-1 and PEPCK levels were suppressed acting as they decreased glucagon levels with increased levels of insulin
What is PGC-1 referred to as? What are the 2 modes of activation when glucagon binds to a cell? Glucagon target gene. Stimulates PGC-1 and PEPCK via phosphorylation of CREB and PGC-1 that acts on HNF4 that further stimulates PEPCK. Refer to slide 19.
Where are the transcription factors Foxo1 and Foxa2 when insulin is added? Why? Outside of the nucleus because AKT phosphorylates Foxo1 and Foxa2 to remove them from the nucleus – “initiates a nuclear exclusion process.” –à(?) it does NOT activate transcription for PEPCK (indirectly)
What are the details involved during a fasted state in relation to PEPCK? Glucagon binds to receptor. PKA phosphorylates CREB. HNF4 is combined with PGC1. Foxo is not phosphorylated. PEPCK is strengthened
What are the details involved during a fed state in relation to PEPCK? Insulin binds to receptor. CREB is not phosphorylated and is diminished as is HNF4 since it lacks the transcription co-factor PGC1. Foxo is phosphorylated and removed from the nucleus via AKT. PEPCK is relieved
Where do all of these events occur? In the structure of chromatin
What are REMs responsible for? Change the density of histones and changes the chromatin structure to render it more or less active for HAT or HDAC.
What activates transcription? Histone acetylation
What does DNA methylation at cytosine infer? Inactive chromatin (reduced transcriptional activity)
True or False. Active and inactive chromatin states are interconverted. True
How do we define epigenetics? Heritable traits (over rounds of cell division or generations) that do not involve changes to the underlying DNA sequence
What did the developmental origins of disease show in children who weighed less at birth and after one year? They were more prone to coronary heart disease (quantified risk of death)
What has epigenetics shown in the studies involving perinatal periods and the influence of environmental factors Developmental pathways are influenced and they induce permanent changes in metabolism and chronic disease susceptibility
What is the difference noticed in rats that were assigned large or small litters in newborns? The large litters had to compete for food – which is a crucial time that effects glucose- affects stimulated insulin secretion later in life based on the pancreas – nutrition deficit newborns were less responsive to insulin (both LL and SL groups were significantly less than control groups)
Were gene expressions different from the control and the two subjects later in life? Yes, Insulin 2 was most different from control vs SL group. Insulin secreted better in control group vs experimental (due to an event perinatally) and it is maintained for a long part of the animals life cycle
What are the 4 mechanisms that lead to epigenetic changes? DNA methylation, Histone modification & DNA binding proteinsRNA-interference
What role does methylation serve in respect to DNA? What areas does methylation usually occur in? It influences the ability of protein to bind to DNA and thus its expression; blocks or reduces affinity of DNA binding proteins and occurs in CPG island clusters.
What is responsible for reading both strands of DNA methylation patters to change the pattern of DNA methylation? What purpose does it serve? DNMT1 (DNA methyltransferase). It ultimately changes patterns of gene expression
What is the classic gene and loci that is regulated by DNA methylation? IGF2 gene, ICR
From maternal to embryo, what blocks DNMT from binding to ICR? What is its other function? What is the overall mode of action? CTCF. Acts as a chromatin boundary (makes regulatory sequences nearby to block their influence – thus, IGF1 is blocked and does not become enhanced
In paternal to embryo, what blocks CTCF from binding to ICR? DNMT (CTCF is also low during spermatogenesis) Expression of IGF2 is observed (although blocks the site of DNA binding protein). CTCF is inhibited by DNA methylation that is an inhibitory process (inhibiting an inhibitor) – which will allow for expression
Who is responsible for the expression of IGF-2? Father
CTCF is present during _____________ and absent during ______________. Spermatogenesis & Oogenesis.
What did the Dutch hunger winters show in subjects who were exposed to famine prenatally? Less DNA methylation – sicker and more susceptible to diseases later in life
How is DNA methylation analyzed? Measure the percentage of cytosines
What must be studied to measure DMR methylation amongst the experimental groups? WCB extracted, which contains a nuclei for appropriate measures
True or False. DNA methylation was statistically significant in individuals exposed to famine late in gestation. False, only early gestation
How long lasting can DNA methylation patterns be? 7-8 decades
What is the reason behind low methylation in early pregnancy under nutrition offspring? Restricted nutrition has less methyl groups – which would need to be donated in order to increase methylation