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Genetics > Lecture 4 > Flashcards

Lecture 4 Flashcards

1
Q

How many RNA polymerases exist in eukaryotes?

A
  1. RNA Poly I/ II and III
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2
Q

What is an active enzyme complex called?

A

Holoenzyme

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3
Q

What is the function of RNA Poly I and III?

A

Ribosomal and tRNA synthesis

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4
Q

What is the function of RNA Poly II?

A

Protein coding genes

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5
Q

What are they key steps of the Transcriptional Process?

A

Initiation: Recruits Polymerase
Pause Release
Elongation

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6
Q

What is the assembly of Polymerase called?

A

Pre-Initiation complex

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7
Q

What is a Transcription Factor?

A

Protein involved in transcriptional initiation or elongation or in their regulation

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8
Q

What is a promoter?

A

Regulatory DNA sequence. Defines transcription start site

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9
Q

What is the TATA box?

A

AT-rich sequence: Recruites TATA binding protein (TBP) and (TBP associated factor) TAF

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10
Q

What do TAFs do?

A

Mediate contacts to other transcription factors

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11
Q

What is the assembly of the pre-initiation complex?

A

Promoter recognition: TFIID recognizes promoter and binds via (TATA binding protein) TBP
Assembly of Transcription factors:
RNA PolyII is recruited to promoter region.
TFIIH helps unwind the DNA
Formation of Pre-initiation complex by all transcription factors and RNA Poly II
Initiation: TFIIH phosphorylates C-terminal RNA Poly II and initiates transcription elongation

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12
Q

How many bp are transcribed after the first transcription elongation? And why is that?

A

Only about 20-30. Pause-release -> second phophorylation at CTD occurs. This is done to keep genes “ready to be transcribed” -> transcription can occure faster if genes are already prepared

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13
Q

When does splicing occure?

A

Co-transcriptionally

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14
Q

What is the poly-A signal used for?

A

Transcription termination

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15
Q

What is ATP used for in Transcription?

A

As hydrolysis target in transcription initiation

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16
Q

What is the negative control of transcription regulation at the promoter level?

A

Activation by absence of repressor, but repressor needs to be constantly present

17
Q

What is the positive control of transcription regulation at the promoter level?

A

Activation by presence of activator, activator only neden when transcription occurs

18
Q

What are promoter functions and where do they lie?

A

Next to transcription start site and they are needed for RNA pol II positioning, and can bind repressors (regulation)

19
Q

What does gene control of transcription factors depend on?

A

Availability of factor
Accesibility of DNA
Activity of factor

20
Q

What are common features of transcription factors?

A

DNA-binding
binds DNA as dimers
co-operate with other factors
mediate transcription activation

21
Q

How does the glucocorticoid receptor work?

A

Steroid replaces nucleosome and opens a binding site for Transcription factor to activate transcription (normally blocked by nucleosome)

22
Q

What is a co-activator?

A

Does not bind DNA itself but mediates transcription by interacting with Transcription factors

23
Q

What is the most ubiquitous co-activator of transcription

A

Mediator Complex

24
Q

What does the mediator complex do?

A

Mediator complex receives signals from Transcription factors and transcmits them to RNA poly II

25
Q

Can Transcription be fine tuned?

A

Yes by several factors working in tandem.

26
Q

What are enhancers?

A

Regulate transcription far away from promoter

27
Q

How do enhancers act?

A

Regulate through proximity in space

28
Q

How do enhancers work?

A

Chromatine remodleing or direct interaction with transcription machinery

29
Q

What is a multi-TF complex on enhancercalled?

A

Enhancosome

30
Q

What is a super enhancer?

A

Multiple enhancers acting together
high density of TF binding sites
increased transcriptional activation
sustained transcriptional activation

31
Q

Transcription in 5 steps

A

1: Transcription factor recruitment and remodeling of Nucleosomes
2:Pol II recruitment and progression to start site
3: signal-pause release, beginning of Transcription

32
Q

What are transcription factories?

A

local concentrations of Transcription factors, RNA Poly and co-activators etc in the nucelus

33
Q

How does MYC become hyperactive in cancer?

A

By interchromosomal translocation of enhancers -> leads to enhancer duplication -> increase in transcription

Genetics (24 decks)

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