Eukaryotic Transcription Regulation

Question 1

what determines the startpoint for transcription?

Answer 1

basal apparatus

Question 2

what determines the frequency of transcription?

Answer 2

activators

Question 3

coactivators

Answer 3

connect activators to basal factors
- some have HAT activity and connect to SWI/SNF complexes

Question 4

how do repressors work in eukaryotes?

Answer 4

• sequestered in the cytoplasm
• concentration driven by competition

Question 5

what is the role of DNA-binding domains?

Answer 5

to bring the transcription-activation domain into the vicinity of the promoter
- DNA binding activity and transcription-activation are carried by independent domains of an activator

Question 6

transcriptional activation motifs

Answer 6

make contact with basal factors and recruit them to the promoter

Question 7

heat shock factor DNA binding domain

Answer 7

• histone H1
• helix turn helix

Question 8

helix-turn-helix

Answer 8

triple helical cluster reinforced with beta strands
- antennapedia phenotype

Question 9

basic leucine zipper proteins (bZIP)

Answer 9

coiled-coil dimerization domain plus a basic DNA interaction domain
- GCN4

Question 10

basic helix-loop-helix (bHLH)

Answer 10

involved in differentiation of muscle cells

Question 11

zinc containing DNA binding domains

Answer 11

• zinc fingers
• bimetal thiolate cluster
• nuclear receptors

Question 12

zinc fingers

Answer 12

Cys2-His 2 coordinated by a single zinc ion
- Zif268

Question 13

bimetal thiolate cluster

Answer 13

2 zinc ions coordinated by 6 cysteines
- GAL4

Question 14

nuclear receptors

Answer 14

• steroids and related horomones
• bind ligand to activate
• 2 zinc molecules with 4 cysteins
• gluccorticoid receptor

Question 15

why do nuclear receptors have 2 zinc modules?

Answer 15

one for DNA interactions and the other for dimerization

Question 16

how many zinc fingers fit into the major groove?

Answer 16

3

Question 17

acidic activation domains

Answer 17

• cluster of negative charges
• bulky hydrophobic residues
• amphipathic
• VP16 - mammalian herpes simplex virus

Question 18

what is a major class of domains found in yeast?

Answer 18

acidic activators

Question 19

glucocorticoid receptor

Answer 19

across the cellular membrane and binds to the GR. This disrupts the interaction between Hsp90 and the GR and allows the hormone/receptor complex (HR) to translocate to the nucleus where it dimerizes and binds to the promoter to target genes activating transcription.

Question 20

taxmoxifen

Answer 20

• used to fight breast cancer
• causes helix 12 to block p160 binding

Question 21

ligand binding domain of the estrogen receptor

Answer 21

helix 12 rotates when ligand binds
- allows p160 to bind later

Question 22

steroid activators

Answer 22

do not directly recruit members of the preinitiation
complex. Instead, they make contact with coactivatorscoactivators, which in turn,
recruit basal factors.

Question 23

mode of activator function

Answer 23

1. p160 recruits HAT activity
2. the estrogen receptor first recruits the CBP in the early stages of transcription and later recruits the mediator

Question 24

what do the following complexes have in common? p160, PCAF, and p300

Answer 24

all have HAT activity

Question 25

glucocorticoid, mineralcorticoid, androgen, and progesterone

Answer 25

- form homodimers - all recognize TGTTCT - half sites are palindromes and spacing determines the element - head to head receptors - exception in TGACCT in estrogen

Question 26

thyroid, vitamin D, retinoic acid, 9-cis-retinoic acid

Answer 26

- form heterodimers, with the exception of 9-cis which is a homodimer - recognize half elements TGACCT as direct repeats - spacing influences recognition - head to tail

Question 27

9-cis-retinoic acid spacing

Answer 27

1 bp

Question 28

vitamin D spacing

Answer 28

3 bp

Question 29

thyroid spacing

Answer 29

4bp

Question 30

retinoic acid spacing

Answer 30

5 bp

Question 31

SMRT co-repressor

Answer 31

- thyroid and retinoic acid receptors bind to the SMRT corepressor at the promoter in the absence of ligand - binding reduces affinity for the corepressor and allows binding to coactivators

Question 32

what triggers the glucosinolate pathway in plants?

Answer 32

insect feeding

Question 33

glucosinolate pathway

Answer 33

- insect feeding - synthesis of jasminate horomone - activates glucosinolate pathway - promoter repressed if no feeding, resulting in chromosome condensation and repression - if there is feeding, Med25 and others reduce repression and start the estrogen cycle