Regulation II

Question 1

steroid hormone and thyroid hormone receptors are examples of?

Answer 1

transcription factors

Question 2

what do steroid hormones bind too? how would you classify what they bind too? how do they affect transcription?

Answer 2

nuclear receptors; transcription factors; they either activate or inhibit transcription of specific genes

Question 3

what do the nuclear receptors bind too, the ones that steroid hormones bind too?

Answer 3

Hormone response elements

Question 4

what are hormone response elements?

Answer 4

DNA regulatory sequences

Question 5

what is the effect of nuclear receptor binding?

Answer 5

induce or repress transcription of target genes

Question 6

what happens after you have nuclear binding?

Answer 6

Transactivation domain binds to co-activator proteins that interact with the basal transcription complex and nuclear localization signal domain directs the complex to the nucleus

Question 7

what are thyroid hormone receptors?

Answer 7

gene-specific transactivation factors but form heterodimers that constitutively bind to a regulatory DNA sequence in the absence of hormone ligand and repress transcription

Question 8

what do thyroid hormone receptors form?

Answer 8

heterodimers that constitutively bind to a regulatory DNA sequence in the absence of hormone ligand and repress transcription

Question 9

what does the thyroid hormone receptor form a heterodimer with?

Answer 9

retinoid X receptor (RXR) that binds to thyroid response elements and to co-repressors, this inhibits gene expression

Question 10

what is the effect of the thyroid binding to the thyroid receptor?

Answer 10

confirmation change, TAD binds coactivators and initiation of transcription

Question 11

describe the transcription initiation from thyroid hormone binding?

Answer 11

Thyroid hormone bind to receptor dimer changes confirmation to TAD binds co-activators to transcription initiation

Question 12

because transcription factors can be specific, they can have several unique structural motifs, name these 4?

Answer 12

Zinc fingers
b-zip proteins (incl. leucine zippers)
Helix-turn-helix
Helix- loop- helix

Question 13

what is best to note about structural motifs?

Answer 13

Each have a distinct recognition site (DNA-binding domain) that binds to a specific sequence of nucleotides

Question 14

what is ferritin?

Answer 14

protein involved in the storage of iron within cells

Question 15

when is ferritin synthesized?

Answer 15

when iron levels increase

Question 16

in terms of regulation at the translation level, how is ferritin translated?

Answer 16

mRNA for ferritin has an IRE consisting of a hairpin loop that bind to a regulatory protein called the iron response element-binding protein (IRE-BP), when iron levels are increased

Question 17

what happens when IRE-BP does not contain bound iron in the regulation of translation for ferritin?

Answer 17

it binds to IRE preventing translation

Question 18

what happens when IRE-BP binds iron?

Answer 18

it dissociates, and the mRNA is translated.