Eukaryotic Gene Expression Regulation 2 (L10)

Question 1

In the absence of a hormone, hsp90 keeps the gluococorticoid receptor where?

Answer 1

In the cytosol

Question 2

What type of protein is hsp90?

Answer 2

A chaperone protein

Question 3

What is the general role of chaperone proteins?

Answer 3

To prevent inappropriate interactions

Question 4

Glucocorticoid hormone enters the cell via what mechanism?

Answer 4

Diffusion

Question 5

The process of gluococorticoid

Answer 5

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

Question 6

What does the glucocorticoid receptor bind to GRE as?

Answer 6

A dimer, one member of the dimer binds to each half seqeuence

Question 7

Steroid hormones receptors are what type of protein?

Answer 7

Zinc finger proteins

Question 8

What are the two functions of Zinc fingers?

Answer 8

1) Binding to DNA

2) Dimer formation

Question 9

Do response elements for different steroid hormone receptors have similar DNA sequences?

Answer 9

YES

Question 10

What does the glucocorticoid receptor probably do?

Answer 10

1) causes chromatin remodelling

2) Binds to mediator

Question 11

What is the involvement of AP1 with the glucocorticoid receptor?

Answer 11

AP1 increases general chromatin accessibility and helps glucocorticoid receptor bind to the GRE

Question 12

Why don’t all cells respond to one hormone?

Answer 12

Insensitive cells don’t contain hormone receptor, e.g. liver cells don’t respond to progesterone as don’t have receptor for it.

Question 13

Specificity depends on what?

Answer 13

The DNA sequence of the response element and the amino acid sequence of the binding domain.

Question 14

What do fibroblast cells normally form?

Answer 14

The extracellular matrix

Question 15

What do fibroblast cells differentiate into?

Answer 15

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.

Question 16

What are somites?

Answer 16

Segmented blocks of cells that form along the side of the notochord in vertebrate embryos. Cells from somites form vertebrae, ribs, muscle and limb.

Question 17

What do MyoD and Myf5 do in muscle formation?

Answer 17

They convert undifferentiated somite cells to undifferentiated muscle precursors: MYOBLASTS
This process is an example of determination precedes differentiation.

Question 18

The myogenin gene is transcribed in myoblasts which causes?

Answer 18

myoblasts to fuse and form multinucleate mature muscle cells: MYOTUBES.

Question 19

The four transcription factors (Oct4, Soxa, Klf4, Myc) in combination can reprogramme fibroblasts to form what?

Answer 19

Induced pluripotent stem cells (iPS cells)

Question 20

Three transcription factors (Pdx1, Ngn3, MafA) in combination can reprogramme exocrine cells of the pancreas to what?

Answer 20

Islet beta-cells

That produce insulin- could help cure diabetes.

Question 21

When iron concentration is high, cell needs to store the iron, Ferritin mRNA is

Answer 21

translated

Question 22

When iron concentration is low, ferritin mRNA is

Answer 22

not translated

Question 23

When iron concentration in cell is low, cell needs to take up more iron: transferrin receptor mRNA is

Answer 23

stable

Question 24

When iron concentration is high, cell does not need to make up more iron: transferrin receptor is

Answer 24

degraded