Transcription factors

Question 1

What is meant by Gene expression ?

Answer 1

DNA undergoes TRANSCRIPTION to form RNA which translates to PROTEIN

Question 2

What is meant by the ‘Central Dogma’ ?

Answer 2

DNA makes RNA makes PROTEIN (Crick)

Question 3

What are Eukaryotic RNA Polymerases and how many types are there?

Answer 3

• Enzymes that perform transcription (of genetic information) from DNA to RNA.
• 3 types of Eukaryotic RNA Polymerases

Question 4

Where are the RNA Polymerases located ?

Answer 4

Nucleus

Question 5

What is the function of RNA Polymerase I

Answer 5

To transcribe rRNA (rRNA is essential for transcription)

Question 6

What is the function of RNA Polymerase II

Answer 6

To transcribe …1) Eukaryotic genes 2) Protein encoding genes (mRNA)

mRNA = translated into Protein and genes for regulatory genes e.g; miRNA

Question 7

What is the function of RNA Polymerase III

Answer 7

To transcribe structural RNAs

Question 8

Name 3 examples of structural RNA ?

Answer 8

1) 5S pre-RNA
2) pre-tRNA
3) snRNA

Question 9

What is a ‘Transcription factor’ ?

Answer 9

A protein that binds to DNA and helps recruit the appropriate polymerase. Therefore controls the rate of transcription of genetic information from DNA to RNA

Question 10

How do TF’s help to recruit the appropriate polymerase?

Answer 10

1) One or more TF binds to DNA regulatory sequences
2) Recruits co-factors
3) Therefore; allows efficient recruitment of DNA Polymerase

Question 11

Name 3 examples of co-factors ?

Answer 11

1) Activators
2) Co-activators
3) General factors

Question 12

What is the role of Activators ?

Answer 12

1) Bind to DNA at ENHANCERS
2) DNA folds and enhancer = brought into contact with INITIATION COMPLEX
3) Activator proteins interact with initiation complex therefore INCREASES RATE OF TRANSCRIPTION

Question 13

What is the role of Co-Activators ?

Answer 13

Transmits signals from activator proteins to general factors

Question 14

What is the role of General factors ?

Answer 14

Initiates Transcription. by;

1) Positioning RNA polymerase at start of protein-coding sequence
2) then; releasing the polymerase to initiate transcription

Question 15

What is Estrogen ?

Answer 15

Type of steroid hormone (female sex hormones & corticosteroids)

Question 16

Role of Cholesterol in producing Estrogen ?

Answer 16

1) Cholesterol = modified by enzymes to make steroid hormones (Estradiol) in the ovaries

Question 17

Name 3 types of Estrogen and which is the most potent in the body ?

Answer 17

1) Estrone (E1)
2) Estradiol (E2) = Most potent
3) Estriol (E3)

Question 18

What does the Estrogen- receptor complex bind to?

Answer 18

A 38-base pair estrogen responsive element (ERE) consensus sequence.

Question 19

What does the (ERE) consensus sequence contain ?

Answer 19

The inverted repeat; 5’-GGTCAnnnTGACC-3’ - this causes gene expression

Question 20

Name the primary function of Estrogen

Answer 20

For development of the female secondary sexual characteristics. e.g; Breasts, Endometrium, Menstrual cycle AND for Stimulation of cell Proliferation

Question 21

Name 4 organs Estrogen has an effect on

Answer 21

1) Bones
2) Brain
3) Heart
4) Liver - Increases good cholesterol (HDL), Decreases bad cholesterol (LDL)

Question 22

What are the 2 types of Estrogen receptors and where are they located?

Answer 22

ERalpha (coded for by ESR1) and ERbeta(coded for by ESR2) - they are located on seperate chromosomes

Question 23

What is the action of Estrogen in the cell dependent upon ?

Answer 23

On the presence/type of estrogen receptor on the target cell

Question 24

In what tissues/cells can ERa be found ?

Answer 24

Endometrium, Hypothalamus, Breast cancer cells, Ovarian Stroma cells

Question 25

In what tissues/cells can ERb be found ?

Answer 25

Bone, Brain, Heart, Kidney, Lungs, Intestinal mucosa, Prostate, Endothelial cells

Question 26

What are some harmful effects of Estrogen ?

Answer 26

Increases risk of cancer in the Breast and Uterus

Question 27

What are Antiestrogens ?

Answer 27

Estrogen antagonist that inhibit estrogen binding

Question 28

What are SERMs ?

Answer 28

Selective Estrogen Receptor Modulators -can act as Agonists and Antagonists

Question 29

Why is the structure of ligand bound to the ER important ?

Answer 29

Dependent on the structure, this influences the ability of the ER to interact w/other transcriptional co-factors

Question 30

Name 3 types of major SERMs

Answer 30

1) Tamoxifen
2) Raloxifene (a new SERM)
3) Clomifene

Question 31

Uses of Tamoxifen ?

Answer 31

ER Antagonists - Inhibits estrogen-dependent growth, of breast cancer (In breast tissue)

Partial Agonists - In Bone and Uterus endometrium - Stimulates growth

Question 32

Risks of Tamoxifen ?

Answer 32

1) Binds to ER causing endometrial cell proliferation = increase cancer risk
2) Increases risk of blood clot

Question 33

Uses of Raloxifene ?

Answer 33

Antagonists -In Breast and Endometrium - reduces cancer risk

Agonists - In Bone - Decreases bone resorption = Osteoporosis treatment

Question 34

Uses of Clomifene ?

Answer 34

Antagonists -In Hypothalamus and Anterior pituitary gland - Increases release of Ovulation hormones

Agonists - In Ovaries - Treatment for Infertility