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C Bio > Controle of Gene Expression (8) > Flashcards

Controle of Gene Expression (8) Flashcards

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Biology 101 flashcards
1
Q

housekeeping genes

A

expressed in all cells all the time, routine functions

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2
Q

What are 3 conditions that cause certain gene expression?

A

cell begins to differentiate
cells with specialized functions
conditions change

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3
Q

regulatory sequences

A

DAN which through the action of specific PROs control the activity/expression of genes

PRO coding
upstream
diffs in regulatory genes among species

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4
Q

where are regulatory sequences located in respect to a gene?

A

upstream

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5
Q

What are the diff levels/way that genes are regulated?

A

transcription
processing
translational
post translational

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6
Q

transcription level regulation

A

o if & how often a gene is transcribed

One gene can be transcribed more than another, rate of transcription

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7
Q

processing level regulation

A

o diff mRNAs made from a given gene

Stored or translated immediately

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8
Q

translational level

A

how much of the mRNA is made into PRO (mRNA lifetime)

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9
Q

post-translation

A

PRO lifetime

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10
Q

What causes RNA pol II to transcribe some genes more than others?

A

regulatory sites on the DNA & presence of transcription factors

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11
Q

transcription factors & what domains are assoc with the PRO?

A

DNA-binding PROS that regulate transcription

DNA binding domain
activation domain (binding site for other PROs) 
binding site for a second subunit to form a dimer
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12
Q

What regulatory PROs are dimers? (2)

A

helix-loop-helix motif & leucine-zipper motif

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13
Q

what PROs are involved in regulating gene expression?

A

zinc-finger motif
helix loop helix motif
leucine zipper motif

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14
Q

zinc finger motif

A

multi finger-shaped projections of PRO fit into major grooves of DNA
ONLY monomers enables fitting into grooves

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15
Q

helix loop helix motif

A

produce transcription factors, homo & heterodimers

Functions as a dimer

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16
Q

leucine zipper motif

A

2 helices zipped together, binds to small region of DNA

Dimer

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17
Q

what regulatory PRO contains helices

A

leucine zipper motif

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18
Q

where is the core promoter located in respect to the gene?

A

-1 to -40 bases from the start codon

upstream

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19
Q

what does RNA pol I require to bind to genes?

A

transcription factors

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20
Q

what recognizes the core promoter?

A

DNA binding PROs: general transcription factors comprising of the pre-initiation complex
TBP: recognizes TATA 30 bases upstream
TAF: grp of general transcription factors PROs for RNA pol II
RNA pol II: produces the RNA

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21
Q

What PROs are apart of the pre-initiation complex?

A

TBP
TAF
RNA pol II

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22
Q

TBP

A

recognizes the TATA sequences 30 bases upstream from the start gene

pre-initiation complex & core promoter

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23
Q

TAFs

A

a grp of general transcription factors PROs necessary for pol II

pre-initiation complex & core promoter

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24
Q

RNA Pol II

A

produces RNA
positions RNA pol to being process

pre-initiation complex & core promoter

25
Q

What complex is required to start expression?

A

pre-initatiation complex

26
Q

proxmial promoter

A
  • 40 to -150 bases away

CAAT & GC boxes bind to transcription factors such as NF1 which recruits a co-activator needed for Pol I to work

also recruits general transcription factors

27
Q

What is the role of NF1?

A

binds to CAAT & GC boxes to recruit a co-activator required for RNA pol to work

28
Q

what does the proximal promoter regulate?

A

frequency of transcription

29
Q

what does the core promoter regulate?

A

whether or not transcription can occur

30
Q

how is the proximal promoter inactivated?

A

cytoseins in the GC box are methylated

gene is transcriptionally inactive

31
Q

distal promoter

A

-500 to - 100 bp

contains response elements

32
Q

response elements

A

DNA sequence that binds to PROs called specific transcription factors recruit transcription factors such as, HLH, zinc finger etc.

33
Q

specific transcription factors

A

activate or repress transcription activity to a specific gene or multiple genes

34
Q

what are the 3 promoters?

A

core promoter
proximal promoter
distal promoter

35
Q

how is gene activity regulated?

A

presence or absence of specific transcription factors

36
Q

how are transcription factors activated?

A

dimerization

37
Q

how does the proximal promoter end transcription?

A

transcription factors recruit repressors

38
Q

proximal promoter can control the ____ & ____ of transcription

A

rate & frequency

39
Q

enhancers

A

specific DNA sequences found far from the target gene that bind to specific transcriptional activators & activate gene expression

up or down stream

40
Q

what do enhancers recruit to activate gene expression

A

specific transcription factors

41
Q

insulator sequences

A

separate enhancers from each other by binding to PROs that separate loops

use of structural DNA

42
Q

How do steroids regulate gene expression? Use the ex of Glucocorticoid receptor that controls expression of PEPCK gene.

A
  1. Glucocorticoid (cortisol) is released from the adrenal gland
  2. Passes through liver membrane
  3. Binds to receptor, receptor changes shape
  4. NLS expressed allowing entry into nucleus
  5. Receptor with bound hormone binds to a response element, which binds as a dimer & transcription of PEPCK begins newly made RNA leaves the nucleus
  6. PEPCK PRO made glycogenesis begin
43
Q

How does cortisol trigger the repair of damaged tissue?

A

rapid production of sugar

44
Q

DNA binding domain

A

recognizes a specific DNA sequence

Dimer therefore, recognizes a palindronic sequence

45
Q

What recognizes a palindromic sequence?

A

DNA binding domain

46
Q

activation domain

A

alters transcription usually through a co-repressor or co-activator

47
Q

how does the glucocorticoid receptor turn on the gene?

A

brings in coactivators that:
supply general transcription factors for RNA pol II, TAFs
& alter chromatin binding structure

48
Q

How do transcription factors affect gene transcription?

A

alter histone-binding PRO making the gene accessible to RNA pol
&
acetyl grps –> enable loosening of DNA allowing the transcription factors to have access

49
Q

How does a specific transcription factor work?

A

binds to the response elements in the distal promoter region
recruits co-activator PROs which help the pre-initiation complex work, binds transcription factors & modifies histones
acetyl transferases –> opens up & alters activity
enhances the RNA pol activity

50
Q

What are the aspects of a coactivator?

A

“mediator” + histone modifying enzyme + xhromatin remodeling complex

51
Q

what do coactivators link transcription factors to?

A

general transcription factors needed for transcription

chromatin re modeling enzymes

52
Q

what is the coactivator for the glucocorticoid receptor called?

A

CBP coactivator

a type of histone acetyltransferase (HAT)

53
Q

What does CBP do to histones & what 2 effects does it have?

A

acetylates the lysine residues of histones exposing TATA boxes. TAFII250 acetylates histones as RNA transcribes

reduces strength of histone-DNA interaction
reduces the interactions b/w the histone PROs

54
Q

What complex has its own histone acetyltransferase activity?

A

preinitiation complex

55
Q

histone deacetylases (HDACs) & what effect does it have on gene activity?

A

remove acetyl grps & DNA winds up more tightly

gene activity is silences

56
Q

histone methyltransferases & what effect does it have on gene activity?

A

methyl grps added to histones cause tighter binding

gene activity is silences

57
Q

DNA methyltransferases

A

add methyl grps to DNA at C 5 of cytosine

58
Q

what happens if a cytosine is methylated in a GC Box?

A

silenced forever
“tags” regions of DNA so that they’re utilized (transcribed) differently
reversible process but methylation is “passed on”

59
Q

what are the 3 enzymes involved in transcriptional repression?

A

histone deacetylases (HDACs)
histone methyltransferases
DNA methyltransferases

C Bio (30 decks)

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