Eukaryotic Gene Expression Regulation 2 (L10) Flashcards
In the absence of a hormone, hsp90 keeps the gluococorticoid receptor where?
In the cytosol
What type of protein is hsp90?
A chaperone protein
What is the general role of chaperone proteins?
To prevent inappropriate interactions
Glucocorticoid hormone enters the cell via what mechanism?
Diffusion
The process of gluococorticoid
1) Enters cell by diffusion
2) Hormone binds to glucocorticoid receptor in the CYTOSOL
3) hsp90 dissociates and moves into the nucleus
5) Receptor binds to GRE and activates transcription
What does the glucocorticoid receptor bind to GRE as?
A dimer, one member of the dimer binds to each half seqeuence
Steroid hormones receptors are what type of protein?
Zinc finger proteins
What are the two functions of Zinc fingers?
1) Binding to DNA
2) Dimer formation
Do response elements for different steroid hormone receptors have similar DNA sequences?
YES
What does the glucocorticoid receptor probably do?
1) causes chromatin remodelling
2) Binds to mediator
What is the involvement of AP1 with the glucocorticoid receptor?
AP1 increases general chromatin accessibility and helps glucocorticoid receptor bind to the GRE
Why don’t all cells respond to one hormone?
Insensitive cells don’t contain hormone receptor, e.g. liver cells don’t respond to progesterone as don’t have receptor for it.
Specificity depends on what?
The DNA sequence of the response element and the amino acid sequence of the binding domain.
What do fibroblast cells normally form?
The extracellular matrix
What do fibroblast cells differentiate into?
Into muscle cells when the gene for any four transcription factors (MyoD, myogenin, Myf5 and Mrf4) are artificially expressed in them.
CONCLUSION: they can re programme fibroblast cell development.
What are somites?
Segmented blocks of cells that form along the side of the notochord in vertebrate embryos. Cells from somites form vertebrae, ribs, muscle and limb.
What do MyoD and Myf5 do in muscle formation?
They convert undifferentiated somite cells to undifferentiated muscle precursors: MYOBLASTS
This process is an example of determination precedes differentiation.
The myogenin gene is transcribed in myoblasts which causes?
myoblasts to fuse and form multinucleate mature muscle cells: MYOTUBES.
The four transcription factors (Oct4, Soxa, Klf4, Myc) in combination can reprogramme fibroblasts to form what?
Induced pluripotent stem cells (iPS cells)
Three transcription factors (Pdx1, Ngn3, MafA) in combination can reprogramme exocrine cells of the pancreas to what?
Islet beta-cells
That produce insulin- could help cure diabetes.
When iron concentration is high, cell needs to store the iron, Ferritin mRNA is
translated
When iron concentration is low, ferritin mRNA is
not translated
When iron concentration in cell is low, cell needs to take up more iron: transferrin receptor mRNA is
stable
When iron concentration is high, cell does not need to make up more iron: transferrin receptor is
degraded
