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Test 2 FTM > Lecture 31 + DLA 23 > Flashcards

Lecture 31 + DLA 23 Flashcards

1
Q

What are the purpose of repressor proteins in bacteria?

A

bind to an operator region and prevent RNA

polymerase from initiating transcription

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2
Q

What are the purpose of activator proteins in bacteria?

A

bind to or near an operator region and allow RNA

polymerase to initiate transcription

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3
Q

What is the purpose of the operator region in bacteria?

A

The operator is a sequence of DNA which is a binding site for specific proteins that help to regulate gene expression

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4
Q

When lactose is present E.Coli produces three protein products…. which are

A

lacZ

LacY

LacA

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5
Q

What does lacZ do?

A

it is a beta-galactosidase

digests lactose into glucose and galactose

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6
Q

What does LacY do?

A

it is a permease

allows for activate transport of lactose across the cell membrane

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7
Q

What does lacA do?

A

it is a transacetylase

it transfers an acetyl group from acetyl coA to beta-galactosides (acetylegalactose)

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8
Q

What does the lacI gene do?

A

encodes a repressor protein that shuts the system down when lactose is not present

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9
Q

how does the Lac operon get turned on?

A

this is an inducible system, thus lactose must be present

when lactose is not present the repressor is bound to the operator, thus RNA poly cannot bind

when lactose is present, the formation of allolactose is formed and will bind to the repressor. this leads to conformation change and thus RNA poly can bind.

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10
Q

What happens if LacZ, LacA, and LacY are mutated?

A

they will be non-functional proteins

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11
Q

what if LacP is mutated?

A

if the promoter is non-function than RNA poly cannot bind and the gene is not going to be expressed.

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12
Q

What if LacO is mutated.

A

If the operator is mutated, that means that the repressor cannot bind, thus the system cannot be turned off

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13
Q

What if LacI is mutated?

A

The repressor would not be functional, thus unable to bind to the operator

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14
Q

What if LacI(s) is mutated?

A

super repressor… cannot dissociate from the operator …. thus it is always off

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15
Q

What does cAMP do in regard to lac operon activation?

A

cAMP binds the activator protein CRP (cAMP receptor protein) or CAP (catabolite activator protein), which can then bind lacP to help activate transcription

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16
Q

What bind to the lac promoter?

A

CRP!

RNA poly can then initiate transcription if not glucose is present

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17
Q

What are cis regulatory elements?

A

DNA sites where proteins and trans regulatory elements will bind

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18
Q

What are trans regulatory elements?

A

proteins and transcription factors which will bind to the DNA CIS elements

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19
Q

What are the cis elements?

A
  1. the basal promoter sequence: bind transcription factors that are associated with RNA poly
  2. proximal control regions- bind transcription factors and found near the promoter
  3. enhancer sequence: are far away from the promoter
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20
Q

Why have multiple levels of control? such as basal and upstream promoters?

A

tight regulation

21
Q

transcription factors that bind to enhancer/responce elements must have what three domains?

A
  1. DNA binding
  2. dimerization domain
  3. Activation/ repressor domain
22
Q

Why different genes have the same response element?

A
  1. provides a mechanism to coordinate gene regulation
  2. allows multiple genes to be regulated together
  3. allows different genes to be turned off or on at the same time
23
Q

What are the three modes of repression transcription factors can have?

A
  1. competition
  2. quenching
  3. blocking
24
Q

Explain the competition mode of repression?

A

the repressor protein will compete with the activator protein in order to bind to the enhancer region

if repressor binds transcription is reduced.

25
Q

explain quenching (mode of repression)

A

Occurs when the repressor protein bind to and interferes with the DNA binding domain of an activator protein

26
Q

explain blocking (mode of repression)

A

This occurs when the repressor protein binds to the activation domain of an activator protein and prevents it from interacting with the basal transcriptional machinery

27
Q

What is hypoxia?

A

It is the reduction in the normal level of tissue oxygen tension

can occur during pathophysiological responces

28
Q

What is HIF-1?

A

the activity of that protein leads to the upregulation of genes that are involved with cell survival, glucose metabolism, angiogenesis, cancer progression, and invasion.

in low oxygen environments

29
Q

What must bind to the HRE gene?

A

HIF1(alpha) and HIF1 (beta) transcription factors must dimerize, then bind to a specific DNA sequence called the Hypoxia Response Element

30
Q

Where is HRE found?

A

it is found up stream on many different genes

31
Q

What kind of gene is HIF-1 alpha

A

inducible

O2 sensitive

32
Q

what kind of gene is HIF-1 beta?

A

constitutive

33
Q

What is the role of prolyl hydroxylase?

A

In high oxygen environments the HIF-1 alpha is hydroxylated and quickly degraded in the proteosome

In no to low oxygen, HIF-1 alpha is stabilized, moved to the nucleus and dimerizes with HIF-1 beta to activate multiple genes that enhance oxygen delivery

34
Q

What is the glucocorticoid receptor do?

A

This is a zinc- finger type

The activated GR complex up-regulates the expression of anti-inflammatory genes in the nucleus and represses the expression of pro-inflammatory proteins in the cytosol

35
Q

How is the glucocorticoid receptor activated?

A
  1. when cortisol is absent the GR is held in the cytoplsm as part of an inactive protein complex
  2. when cortisol binds to GR, it dissociates from regulatory complex
  3. The GR forms a dimer
  4. the dimer moves to the nucleus and binds to HRE
  5. this leads to gene expression if targeted genes
36
Q

What is the myc/max system?

A

it is a regulatory mechanism for switching between gene activation and repression

37
Q

What is myc?

A

myc has a transcriptional regulation domain, but it cannot bind to DNA until it dimerizes

does a lot with regulation with the cell cycle

38
Q

In the absence of Myc?

A

Max forms a homodimer and it represses gene expression

cell cycle is inhibited

39
Q

In non-proliferating cells what is the expression of myc and max

A

Max = expressed

myc = not expressed

40
Q

In the presence of myc?

A

a myc/max heterodimer is formed to activate gene expression

cell proliferation

41
Q

What are the different families of hemoglobin?

A
  1. fetal hemoglobin = two alpha and two gamma chains
  2. hemoglobin A = two alpha and two beta
  3. hemoglobin A2 = two alpha and two tetra chains
42
Q

What are the two types of interfering RNA’s

A
  1. miRNA = regulated gene expression by inhibiting mRNA translation
    mostly endogenous
    derived from ds pre-miRNA species
  2. siRNA = regulates expression by mRNA degradation
    mostly exogenous
    derived from long dsRNAs and ‘random’ processing
43
Q

What does drosha do?

A

long pri-miRNAs are processed to pre-miRNA hairpin strucutres by drosha

44
Q

what does exportin 5 do?

A

transports pre-miRNA to cytoplasm

45
Q

What does Dicer do?

A

further processes them to single stranded RNA and initiates the formation of the RNA-induced silencing complex (RISC)

46
Q

What does RISC do?

A

will bind imperfectly to the target mRNA which inhibits translation

47
Q

what protein processes long dsRNA into siRNA

A

Dicer

48
Q

How do miRNA’s regulate gene expression?

A

The translational machinery cannot interact with the 5 prime cap structure, thus mRNA is not translated

49
Q

How do siRNA’s regulate gene expression?

A

Perfect pairing of siRNA with mRNA within the RISC complex will activate RISC endonuclease AGO2 activity & mRNA will be cleaved and not translated

Test 2 FTM (28 decks)

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