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Molecular Biology BIOL10221 > General mechanism of Transcription > Flashcards

General mechanism of Transcription Flashcards

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1
Q

what is a coding strand

A

aka sense strand
5’ to 3’
has same sequence as RNA that’s produced

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2
Q

what is template strand

A

aka antisense strand
3’ - 5’
has complementory sequence to the RNA that’s producced

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3
Q

what does a promoter do

A

tells RNA Polymerase:
where to start transc
what direction to transc in

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4
Q

what are the sequences that an RNA pol recognises on a promoter

A

-10 = TATAAATG
-35 = TTGACA

only recognises this sequences then it knows what to attach to and which direction to go in

see onenote for diagram

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5
Q

what are the 3 phases of transcription

A

initiation
elongation
termination

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6
Q

main enzyme involved in transc

A

RNA polymerase

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7
Q

initiation

A

RNA pol binds to promoter
seperates strands for DNA
template strand used to make mRNA strand

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8
Q

elongation

A

using the template strand, complementary mRNA strand is produced
complementary nucleotides added to form strand
(remember not T but U in RNA strand)

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9
Q

termination

A

stop signal from terminator gene
mRNA released from trancription complex

this strand is called pre mRNA (not yet ready to leave nucleus

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10
Q

prokaryotic RNA polymerase enzyme subunits

A

sigma
2 alpha
2 beta (beta and beta’)
omega

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11
Q

prok RNA pol subunits function: sigma

A

promoter recognition
recognises the -35 and -10 boxes

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12
Q

prok RNA pol subunits function: alpha

A

assembly and transcription activation

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13
Q

prok RNA pol subunits function: beta

A

catalysis (adding nucleotides to growing RNA chain)
termination

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14
Q

prok RNA pol subunits function: omega

A

involved in assembly
folding
in some genes and not others

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15
Q

difference between RNA holoenzyme and core enzyme

A

holoenzyme - whole thing with all subunits

core enzyme - when polymerase starts transcribing, sigma subunit breaks off leaving the core enzyme (alpha, beta and omega units only)

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16
Q

why does sigma subunit need to break off`

A

only needed during inititation to detect the start codon

after this, the enzyme must turn non-specific for any particular sequence
so polymerase only has general affinity for DNA

17
Q

euk RNA polymerase, the 3 types and their functions

A

pol I = makes ribosomal RNA genes

pol II = makes protein coding genes (mRNA)
and small nuclear RNA (snRNA)

pol III = transfer RNA (tRNA)
also, rRNA and snRNA

18
Q

euk RNA Pol II features

A

large enzyme
~10 core subunitsk

19
Q

how does euk rna pol II interact with the promoter sequence?

A

must be recruited by transcription factors
e.g. TF2D (aka TFIID so basically transcription factor for rna pol II)

20
Q

what is function of TFIID and what is it made up of

A

allows the RNA pol II to recognise and bind to promoter site
TFIID is a multisubunit protein
made of these subunits:
TATA binding protein (TBP) = the bit that acc binds to the promoter site
and
TBP Associated factors (TAFs)

21
Q

what is the TFIID similar to

A

similar sequence to the sigma subunit
promoters are very TA rich (similar to the -10 sequence in prok promoters)

22
Q

other transcription factors needed in eukaryotes during initiation

A

TFIIA - helps TFIID bind

TFIIB - measures distance between core promoter sequence (the AT rich one) and the transcritption start site

23
Q

other transcription factors needed and their general functions

A

TFII E, F, H, J and K

  • blocks non specific binding of pol II to DNA (liek sigma)
  • promoter clearance > starts to elongate and make chain
  • helicase > unwinding the DNA
  • procesivity > so once it starts, it continues to full transribe the chain
  • DNA repair > scanning chain for errors and repairs it
24
Q

RNA Pol I main elements

A

core element - contains transcription start site
Upstream control element (UCE)

these 2 bind with protein called Upstream Binding Factor (UBF)
which allows the DNA to kinda loop through

see onenote for diagram

25
Q

what is the main transcription factor for RNA pol I and its components

A

SL1
made up of TBP and pol I specific TAFs

26
Q

difference bwtween the TBP in RNA pol II and RNA pol I

A

in RNA pol II = itneracts with the DNA

in RNA pol I = acts binding site to keep all the TAFs together

27
Q

whats the difference in the transcription start site in a tRNA gene transcribing promoter

A

the promoter is actually ‘downstream’ from the transc start site
so the promoter is within the coding region

promoter is made up of an A box and a B box

see onenote diagram

28
Q

what are the A box and B box bound by in a tRNA gene

A

TFIIIC

29
Q

what are the 2 transcription factors used in the tRNA gene (RNA Pol III)

A

TFIIIC
TFIIIB - made up of TBP and pol III specific TAFs

30
Q

what happens after TFIII B is recruited ?

A

TF IIIC is dispensible
Rna pol III c

31
Q

what happens after TFIII B is recruited ?

A

TF IIIC is dispensible
Rna pol III can then bind without any obstruction

See diagram one note hehe

32
Q

What is the difference between the tRNA genes and the 5s rRNA genes in terms of what factors they use

A

rRNA use an extra factor TFIIIA to recruit TFIIIC
Instead of TFIIIB which is used in tRNA

everything else is pretty much the same

Molecular Biology BIOL10221 (17 decks)

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