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Molecular Biology Test 1 > Chapter 20 - Eukaryotic Transcription > Flashcards

Chapter 20 - Eukaryotic Transcription Flashcards

1
Q

What is required for eukaryotic transcription?

A 
Chromatin must be in an open structure (non-condensed).
Promoter must be nucleosome-free.
Gene must include a core promoter and start point.
RNA Polymerase binds
Basal Transcription Machinery Binds
- Transcription factors that facilitate
binding of the RNA Polymerase to the
promoter.
- TFNX: N=Polymerase I, II, or III and
X=Unique Identifying Letter
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2
Q

Transcription factors (generally)

A

Facilitate binding of the RNA Polymerase to the promoter.
TFNX:
N=Polymerase I, II, or III
X=Unique Identifying Letter

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3
Q

Transcription factors (generally)

A

Facilitate binding of the RNA Polymerase to the promoter.
TFNX:
N=Polymerase I, II, or III
X=Unique Identifying Letter

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4
Q

Enhancer

A

A cis-acting sequence that increases the utilization of
(most) eukaryotic promoters and can function in either
orientation and in any location (upstream or downstream)
relative to the promoter.

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5
Q

Silencer (Repressor)

A

A short sequence of DNA that can inactivate expression of a gene in its vicinity.

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6
Q

RNA polymerase I

A

Synthesizes 5.8S, 18S, and 28S rRNA in the nucleolus.

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7
Q

RNA polymerase III

A

Synthesizes tRNA, 5S rRNA genes, small RNAs in the nucleoplasm.

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8
Q

RNA polymerase II

A

Synthesizes hnRNA in the nucleoplasm; all RNA with the exception of those transcribed by RNA Polymerase I & III

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9
Q

hnRNA

A

Heterogeneous nuclear RNA

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10
Q

hnRNA

A

Heterogeneous nuclear RNA

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11
Q

Promoter includes 2 components:

A
  1. Core promoter

2. Upstream promoter element (UPE)

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12
Q

Transcription from RNA Polymerase I promoter:

A
  1. Upstream binding factor (UBF) binds the UPE
  2. UBF wraps the DNA 360°
  3. Recruits SL1 complex
  4. RNAP I binds UBF/SL1 complex and initiates transcription
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13
Q

SL1

A

Binds core promoter

Includes TATA binding protein (TBP)

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14
Q

Upstream binding factor

A

Bind the Upstream Promoter Element (UPE)

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15
Q

RNA polymerase III has two types of promoters:

A
  1. Upstream promoters

2. Internal promoters

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16
Q

Upstream promoters:

A

Consensus sequences upstream of the start point, bound by transcription factors

Analogous to RNA polymerase II-regulated promoters

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17
Q

Internal promoters:

A

Consensus sequences located within the transcription unit

Supports initiation upstream.

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18
Q

TFIIIC

A 
binds downstream sites.
2. TFIIIB binds start point.
3. TFIIIC is removed from downstream
sites.
4. TFIIIB recruits RNAP III.
19
Q

TFIIIB

A

binds start point.

20
Q

TFIIIC

A

Binds downstream sites

Then removed from downstream sites

21
Q

TFIIIB

A

Binds start point
Removes TFIIIC
Recruits RNAP III

22
Q

TFIIIA

A

Binds downstream sites

23
Q

Basal transcription apparatus

A

RNA Polymerase II + basal transcription factors

24
Q

Core promoter:

A

The shortest sequence that enables binding of the basal transcription apparatus and initiation of transcription

25
Q

RNAP II Core Promoter:

A
  • Initiator (Inr)
  • TATA box
  • Downstream Promoter Element (DPE)
26
Q

Initiator (Inr)

A

Short conserved sequence Py2CAPy5 at the start point.

27
Q

TATA box

A

A-T octomer 25 bp upstream of the start site that positions the RNAP II.

28
Q

Downstream Promoter Element (DPE)

A

Replaces TATA box

29
Q

TAF

A

TBP-associated factors

30
Q

TAF

A

TBP-associated factors

31
Q

TFIID

A

At RNAP II promoters, the TFIID serves as the positioning factor for RNAP and recognition of the promoter.
Composed of TBP and TAFs
Enables the binding of TFIIB

32
Q

TBP

A

Component of positioning factor that is required for RNAP (I, II, III) to bind core promoter.
Binds TATA and TATA-less promoters with equal affinity.
TBP binds the minor groove and forms a “saddle” around the DNA
TBP widens the minor groove and bends-in towards the major groove

33
Q

TFIIB

A 
Binds downstream of TFIID.
Interacts with RNAP II at 2 points:
• RNA exit site 
• Active center.
Interaction with RNAP II orients the enzyme on the DNA
34
Q

TFIIB

A 
Binds downstream of TFIID.
Interacts with RNAP II at 2 points:
• RNA exit site 
• Active center
Interaction with RNAP II orients the enzyme on the DNA
35
Q

TFIIF

A

TFIIF and RNAP II are simultaneously recruited to the TFIID-TFIIB complex.
TFIIF is bound to RNAP II prior to DNA localization of the enzyme.
TFIIF guides RNAP II to and stabilizes it at the TFIID-TFIIB complex.

36
Q

TFIIE

A

Binds the basal apparatus.

TFIIE is required to melt DNA to allow polymerase movement.

Recruits TFIIH.

37
Q

TFIIH

A
  • Helicase activity (DNA melting) which requires interaction with TFIIE.
  • Rapidly repairs damaged DNA to avoid RNAP II stalls.
  • Phosphorylates the C-terminal domain (CTD) of RNAP II (D)
38
Q

TFIIH

A
  • Helicase activity (DNA melting) which requires interaction with TFIIE.
  • Rapidly repairs damaged DNA to avoid RNAP II stalls.
  • Phosphorylates the C-terminal domain (CTD) of RNAP II (D)
39
Q

Promoter clearance

A

Phosphorylation of the CTD is required for release the RNAP II from the promoter (or promoter clearance)

Promoter clearance is required for elongation or transcription of the DNA template strand and extension of the RNA strand.

40
Q

What is required for gene transcription in eukaryotic cells?

A

Chromatin must be in an open structure (non-condensed).

Promoter must be nucleosome-free.

41
Q

Enhancer

A

An enhancer activates the promoter nearest to itself, and
can be any distance either upstream or downstream of the
promoter.
Enhancers are the activating DNA sequence in close
proximity to a gene promoter.

42
Q

Enhancer

A

An enhancer activates the promoter nearest to itself, and
can be any distance either upstream or downstream of the
promoter.
Activate DNA sequence in close proximity to gene promoter.
Usually work in cis with the promoter.
Can be made to work in trans by promoter and enhancer via (1) a protein bridge or (2) interlocking two molecules.
Bound by Co-regulatory Proteins called Activators or Repressors.

43
Q

Activators:

A

Complex of proteins that interact directly or indirectly

with the promoter to initiate gene transcription

44
Q

Repressors:

A

Complex of proteins that prevent gene transcription by

binding to an enhancer

Molecular Biology Test 1 (4 decks)

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