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Hilary Term 1 > The Regulation of Transcription in Eukaryotes > Flashcards

The Regulation of Transcription in Eukaryotes Flashcards

1
Q

What determines the identity and capability of a cell

A

relative abundance of gene products

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2
Q

Describe transcription - the basics

A
  • first step in converting DNA to gene products
  • first step in genotype to phenotype
  • primary regulatory gateway for gene expression
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3
Q

Number of genes per cell:

A

40,000

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4
Q

Number of transcripts per cell:

A

300,000

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5
Q

Number of proteins per cell:

A

1,000,000,000

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6
Q

Describe the amplification of transcripts in a cell

A

~5x

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7
Q

What is the average transcript number per gene?

A

~10

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8
Q

Describe the amplification of proteins in a cell

A

~130x
amplification

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9
Q

What is the average protein number per gene?

A

~1,300

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10
Q

Transcription in eukaryotes is regulated at…

A

three temporally distinct stages

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11
Q

When is transcription in eukaryotes regulated?

A
  • initiation
  • elongation
  • termination
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12
Q

Describe transcription regulation at initation

A
  • transcription factors
  • promoters
  • pre-initiation complex
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13
Q

Describe transcription regulation at elongation

A
  • TFIIS
  • nucleosome/chromatin remodeling
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14
Q

Describe transcription regulation at termination

A

Cleavage and polyadenylation

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15
Q

Describe transcription factors

A
  • the first step transcriptional regulation
  • composed of one or more DNA binding domains and protein-protein interaction domains.
  • bind to short DNA sequence elements (6-20bp)
  • recruit (or block recruitment) of other proteins
  • act as activators or repressors
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16
Q

What the humans genes coding for transcription factors

A
  • 1600 genes
  • 8%
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17
Q

Describe transcription factor gene families

A
  • ~20
  • ~50% of transcription factors in human genome are C2H2 zinc finger transcription factors
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18
Q

Describe the mechanics of transcription factors

A
  • DNA binding domain binds to short sequences in the nucleosome
  • recruit enzymes that alter nucleosomes
  • recruit the PIC
  • GTFs
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19
Q

PIC

A

pre-initiation complex

20
Q

General Transcription Factors

21
Q

List the GTFs

A
  • TFIIA
  • TFIIB
  • TFIID
  • TFIIE
  • TFIIF
  • TFIIH
22
Q

Describe TFIID

A
  • 13 subunit protein complex
  • first recruited component of the pre-initiation complex
  • binds to TBP
23
Q

TBP

A

TATA binding protein

24
Q

Describe the TFIID/TBP complex

A
  • assembles without interacting with DNA
  • TFIID/TBP complex binds DNA via TBP subunit.
  • first stage of pre-initiation complex assembly.
  • can be recruited without a TATA binding site for TBP
25
Q

Describe the TATA box

A
  • consensus sequence is TATAWAW
  • W is either A or T
26
Q

Describe TFIIA

A
  • 3 subunit protein complex
  • binds to TFIID/TBP
  • stabilises TBP interaction with DNA
27
Q

Describe TFIIB

A
  • single protein
  • facilitates recruitment of RNA polymerase II
28
Q

Describe TFIIF

A
  • TFIIF – tetramer
  • Pol II recruited at same time.
  • stabilises Pol II interaction with TFIIB and TFIID
29
Q

Describe Pol II

A
  • RNA polymerase II
  • 12 subunit complex
30
Q

tetrameric

A

two subunit complex

31
Q

Describe TFIIE

A
  • 2 subunit complex
  • recruits TFIIH
32
Q

Describe TFIIH

A
  • 10 subunit complex
  • acts as a DNA helicase
33
Q

Describe the two main function of TFIIH

A
  • opening the promoter to load the polymerase
  • phosphorylating Pol II CTD – promoter escape
34
Q

What happens on pre-initiation assembly?

A
  • phosphorylated Pol II recruits capping enzyme
  • first nucleotide that exits the polymerase gets capped
  • cap protects the RNA from degradation
  • polymerase escapes the promoter and proceeds to transcribe the gene
35
Q

transcription factors act

A

in concert

36
Q

If one transcription factor is mutated

A

All efforts are lost

37
Q

The combinatorial action of transcription factors …

A

specifies cell identity and function

38
Q

Describe elongating polymerases

A
  • not under control of TFs or PIC
39
Q

Describe polymerase gene transcription

A
  • average gene ~20,000 bp: 4.5 mins @ 72 nucleotides sec-1
  • longest gene ~2.2 million bp: 8.5 hours @ 72 nucleotides sec-1
40
Q

What happens if transcription goes wrong?

A
  • elongating polymerase backtracks along the DNA
  • 3’ OH no longer available for extension
  • backtracking cannot be recovered by polymerase
  • RNA must be cleaved to produce new 3’OH
  • once cleaved, polymerase can resume
41
Q

Describe cleavage on elongation backtracking?

A
  • TFIIS
  • creates two domains
42
Q

Describe the average gene

A
  • ~20,000 bp
  • ~90 nucleosomes
43
Q

Describe the longest gene

A
  • ~2.2 million bp
  • 10,000 nucleosomes
44
Q

How does Pol-II navigate nucleosomes

A

with the help of a large cohort of chromatin remodeling enzymes

45
Q

Describe transcription termination

A
  • PAS encoded in the DNA
  • Polymerase transcribes past the PAS
  • CAP complex binds Pol II and PAS in RNA

grabs the polymerase and RNA

46
Q

PAS

A

polyadenylation signal
- AAUAAA

47
Q

CAP

A
  • Cleavage and polyadenylation
    complex
  • 83 proteins

Hilary Term 1 (61 decks)

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