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BMS1. Translation (HAMPSEY) > Eukaryotic Transcription > Flashcards

Eukaryotic Transcription Flashcards

1
Q

DNA sequence promoter elements in eukaryotes and their locations:

A
  • Core promoter (TATA; 25bp from start)
  • Proximal promoter (C/G rich; <120bp from start)
  • Enhancers (>250bp from start)
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2
Q

The “core” promoter region of eukaryotic class II genes typically includes a:

A
  • TATA box
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3
Q

Where is the TATA box in relation to the transcription start site?

A
  • -25
    • 25 base pairs upstream from the transcription start site
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4
Q

Core promoter:

A
  • typically a TATA box
  • -25 from transcription start site
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5
Q

TATA Box:

A
  • core promoter (-25)
  • “nucleation site” for assembly of a transcription complex
  • functionally comparable to the –10 and –35 regions of a bacterial promoter
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6
Q

What is the transcription complex consist of?

A
  1. set of general transcription factors (GTFs)
  2. a RNA polymerase II
  • binds to the nucleation site / TATA box
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7
Q

Proximal promoter location and function:

A
  • <120 bp from start
  • binding site for certain activator proteins
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8
Q

Enhancers location and function:

A
  • typically >250 bp from start
  • function in either orientation
  • function upstream, downstream or even with a gene
  • binding site for transcription activators
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9
Q

Enhancers are the binding sites for transcriptional activators that either:

A
  1. make direct contact components of the RNA polymerase II transcriptional machinery
  2. recruit chromatin remodeling complexes to the regulatory and promoter regions
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10
Q

What promoter region serves as the binding site for “housekeeping” genes?

A
  • proximal promoter region
  • <120bp away from start
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11
Q

How many eukaryotic nuclear polymerases exist?

A
  • 3
    • RNA Pol I
    • RNA Pol II
    • RNA Pol III
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12
Q

What polymerase is specific for rRNA?

A

RNA Pol I

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13
Q

What polymerase is specific for mRNA?

A

RNA Pol II

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14
Q

What polymerase is specific for tRNA?

A

RNA Pol III

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15
Q

RNA Pol III transcribes:

A
  • small RNAs
    • tRNA
    • some snRNAs
    • 5S rRNA
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16
Q

Is there a eukaryotic counterpart to the σ subunit of bacterial RNA polymerases?

A
  • no
  • promoter recognition is conferred by GTFs in eukaryotic transcription
17
Q

How do eukaryotic RNA polymerases recognize specifc DNA sequences (promoters)?

A
  • recruitment of general transcription factors
  • RNA polymerases cannt recognize DNA sequences on their own
18
Q

How many subunits are in RNA Pol II?

A
  • 12 (Rpb1 - Rpb12)
  • some subunits are homologous to each of the bacterial RNA polymerase subunits
19
Q

The general transcription factors (GTFs) specific to RNA Pol II:

A
  1. TFIIA
  2. TFIIB
  3. TFIID (includes TBP, the TATA binding protein)
  4. TFIIE
  5. TFIIF
  6. TFIIH
20
Q

What are the core promoter elements of RNA Pol II?

A
  • BRE (TFIIB recognition element; -35)
  • TATA (TBP binding; -25)
  • INR (initiator; +1)
  • DPE (downstream promotor element; +30)
21
Q

TFIID:

A
  • RNA Pol II - specific GTF
  • contains TBP subunit (binds TATA)
  • recognizes core promoter and tells Pol II where to bind
22
Q

In eukaryotes, the proximal promoter is rich in what bases?

A

C/G

23
Q

What are the two notable features of eukaryotic RNA pol II transcription that do not occur either in bacteria or by RNA pol I or RNA pol III?

A
  • modifications to the 5’ and 3’ ends of the mRNA
  • 5’ 7-methylguanosine “CAP”
  • 3’ Poly-A tail (100-250 amino residues)
24
Q

The 5’ 7-methyguanosinine CAP is added to the mRNA shortly after:

A
  • Initiation
    • just as the nascent mRNA polymer emerges from the RNA pol II enzyme complex
25
Q

Function of 5’ 7-methylguanosinine CAP:

A
  • stabilizes/protects mRNA from nuclease digestion
  • recognized by ribosome
    • thereby facilitating protein synthesis
26
Q

Many activators stimulate transcription by:

A
  • binding GTFs, either to recruit or stabilize their binding to the core promoter.
27
Q

Steps in the assemply of the RNA Pol II Preinitiation Complex (PIC):

A
  • TFIID (TBP subunit) binds to TATA box
  • TFIIB binds, allowing RNA Pol II and TFIIF to form complex
  • TFIIE and TFIIH bind
    • involved in promoter melting clearance (enable RNA pol II to initiate transcription)
28
Q

What two RNA Pol II GTFs are involved in involved in promoter melting clearance?

A
  1. TFIIE
  2. TFIIH

Once completed, transcription begins in 5’ to 3’ direction.

29
Q

The three steps of eukaryotic transcription:

A
  1. initiation
  2. elongation
  3. termination
30
Q

Transcription termination by RNA pol II involves the addition of:

A

a poly(A) tail to the 3’ end of mRNA

31
Q

Eukaryotic transcriptional termination is specified by:

A
  • distinct sequences in the DNA template
  • involves two enzymatic reactions
32
Q

The two enzymatic reactions involved in termination of eukaryotic transcription:

A
  1. endonucleolytic cleavage of the new mRNA transcript
  2. addition of poly(A) tail to 3’ end of mRNA
    • typically 100 – 250 amino acid residues in length
33
Q

Are the 3’ poly-A tail and the 5’ 7-methylguanosine cap encoded by the DNA sequence?

A
  • no
  • they are specific to transcription by RNA Pol II, which produces mRNA
34
Q

Function of the 3’ Poly-A tail:

A
  1. mRNA stabilization
  2. transport of mRNA from the nucleus to the cytoplasm
  3. efficient translation

BMS1. Translation (HAMPSEY) (6 decks)

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