Mod 5 - Gene Expression in Eukaryotes

Question 1

what is the function of methylation in histones?

Answer 1

• Gene activation and repression
• DNA replication
• CH3 group added to lys and his

Question 2

what is the function of acetylation in histones?

Answer 2

• nucleosome assembly
• gene activation
• addition of CH3CO2- group to lysines of core histones

Question 3

what is the function of phosphorylation in histones?

Answer 3

• cell division
• transcription
• chromatin structure
• addition of PO4- to lysines of H1

Question 4

true or false - enhancer regions can be upstream or downstream of promotor regions?

Answer 4

true - orientation too is independent

Question 5

describe the process of activation of transcription by signal transduction

Answer 5

• hormone binds to extracellular receptor
• initiates process of converting ATP to cAMP (secondary messenger)
• activates protein kinase A
• protein kinase A phosphorylates CREB (cAMP regulatory element binding factor)
• CREB then interacts with CBP (CREB-binding protein)
• transcription begins

Question 6

what are some examples of hormones for hormone-dependent gene activation? (5)

Answer 6

• estrogens
• androgens
• corticosteroids
• retinoids
• thyroid hormones

Question 7

describe the process of hormone-dependent gene activation

Answer 7

• steroid hormone freely diffuses through plasma membrane (hydrophobic)
• displaces the HSP90 chaperone protein inhibitor in 2 receptor molecules
• homodimerization occurs - 2 identical monomer receptors come together due to interaction with steroid
• complex now includes 2 receptors and a steroid hormone
• this complex then interacts with the GRE (glucocorticoid response element) and acts as a transcription factor