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Human Molecular B > Lecture 8 - Features Of eukaroyotes > Flashcards

Lecture 8 - Features Of eukaroyotes Flashcards

1
Q

Start point

A

The position on DNA corresponding to first base incorporated into RNA

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2
Q

RNA polymerase I

A

Location: Nucleolus RNA products: pre-rRNA —> 5.8S, 18S and 28S rRNA

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3
Q

RNA polymerase II

A

Location: nucleoplasm RNA products: pre-MRNA and some snRNAs

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4
Q

RNA polymerase III

A

Location: nucleoplasm RNA products: tRNA, 5S rRNA, U6 snRNA (spliceosome) and 7SL RNA (signal recognition particle)

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5
Q

What subunits are present in RNA polymerase I,II,III?

A

Rpb5, Rpb6, Rpb8, Rpb10 and Rpb12

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6
Q

How many subunits in Archaeal?

A

13 subunits

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7
Q

How many subunits in E.coli?

A

5 subunits

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8
Q

TFIIA

A

Subunit: 2 Stabilises TBP and TFIID binding Blocks the inhibitory effects of TAF1 and other proteins

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9
Q

TFIIB

A

Subunit:1 Stabilises TFIID- promoter binding. Contributes to transcription start site selection Help recruit RNA polymerase II TFIIF to the core promoter

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10
Q

TFIID

A

Subunit: 1 and 14 Bind TATA element and deforms the promoter DNA. Platform for the assembly of TFIIB and TAFd. Binds Inr, MTE, DPE and DCE promoter elements

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11
Q

TFIIE

A

Subunit: 2 Helps to recruit TFIIH to the core promoter and is required for promoter melting

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12
Q

TFIIF

A

Subunit: 3 Bind RNA polymerase II and is involved in recruiting the polymerase to the pre-initiation complex. Required to recruit EFIIE and EFIIH to the pre-imitation complex

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13
Q

TFIIH

A

Subunit: 10 Functions in Transcription and DNA repair. It has kinase and helicase activities and is essential for open complex formation

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14
Q

RNA Polymerisation

A

The 3’OH group of the last ribonucleotide asses to the chain reacts with an incoming ribonucleoside 5’triphosphate

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15
Q

How many RNA polymerase a do eukaryotes have?

A

3

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16
Q

Each RNA polymerase in eukaryotes is specifically dedicated to ?

A

rRNA,mRNA or tRNA

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17
Q

Eukaryotic RNA polymerase requires

A

A number of transcription factors Factors to modify chromatin structure to allow RNA polymerase access

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18
Q

RNA polymerase I no of subunits

A

14

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19
Q

RNA polymerase II no of subunits

A

12

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20
Q

RNA Polymerase III number of subunits

A

17

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21
Q

Do eukaryotic RNA Polymerase share subunits?

A

Some but not others

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22
Q

Shared subunits between eukaryotic RNA Polymerase I,II,III

A

Rpb5, Rpb6, Rpb8, Rpb10 and Rpb12

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23
Q

Are there RNA polymerase II homologous in RNA polymerase I and III?

A

Many RNA polymerase II subunits have homologs in RNA polymerase I and/or III

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24
Q

Bacterial RNA polymerase subunits has at least … homolog in each eukaryotic polymerase

A

One

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25
Q

RNA polymerase separates the two strands of DNA in a transient …

A

Bubble

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26
Q

Role of the transient DNA bubble?

A

It uses one strand as a template to direct synthesis of a complementary sequence of RNA

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27
Q

What is the length of transient DNA bubble?

A

12 to 14bp

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28
Q

What is the length of RNA-DNA hybrid within transient DNA bubble?

A

8 to 9bp

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29
Q

What are the 3 stages of transcription ?

A

Initiation, elongation and termination

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30
Q

What is the role of RNA polymerase in transcription?

A

RNA polymerase binds to a promoter site on DNA to form a closed complex RNA polymerase initiates transcription after opening the DNA duplex to form transcription bubble (open complex) RNA polymerase then escapes the promoter During elongation the transcription bubble moves along DNA The RNA chain is extended in 5’ to 3’ direction by adding nucleotides to the 3’end When transcription terminates: The DNA duplex reform.
RNA polymerase dissociates at a terminator site

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31
Q

What are the two forms of transcription initiation ?

A

Focused and dispersed

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32
Q

RNA polymerase cannot initiate transcription from specific start site without the assurance of other proteins such as?

A

Transcription factors

33
Q

What do each RNA polymerase have ?

A

Own specific set of transcription factors

34
Q

What is the role of transcriptional factors that are unique to each RNA polymerase?

A

Factors to assist in locating Pol I, II, III transcriptional start site

35
Q

Approx percentage of vertebrate core promoters that are dispersed promoters?

A

70%

36
Q

Order of assembly of pre-initiation complex?

A

TATA. TFIID TFIIA
TFIIB TFIIF pol II TFIIE.
TFIIH

37
Q

Structure of TATA binding protein (TBP)

A

Saddle shaped and bend DNA by 80 degrees. This is the subunit of TFIID that binds to TATA box

38
Q

What does the interaction between TBP and TATA box Involve?

A

Conformational change in both TBP and the TATA box

39
Q

Where do TBP and TATA interact ?

A

The minor groove

40
Q

Do TBP-associates factors (TAFs) bind promoter elements other than TATA?

A

Yes

41
Q

TBP associated factors (TAFs)

A

Additional proteins present in TFIID are called TAFs TFIID Contain a core set of 13 TAFs.
TAFs are required for high level of transcription and to transcribe genes that lack a TATA box

42
Q

What happens in TATA Less promoters?

A

It is the TAFs that bind to regulatory elements

43
Q

Where does TBP bend the TATA box?

A

C terminal domain of TFIIB

44
Q

What happens in the N terminal domain of TFIIB?

A

Brings the complex to RNA polymerase II and positrons the transcription initiation site in the active site of RNA polymerase

45
Q

What does the RNA polymerase II-TFIIB-promoter complex recruit ?

A

TFIIE which then recruits TFIIH

46
Q

What does the helicase activity of TFIIH unwind?

A

DNA in the vicinity of initiation site

47
Q

What does the TFIIF capture?

A

non-template strand after unwinding

48
Q

Where does the template strand descend to?

A

Active site

49
Q

What is open complex formation?

A

Initiation of transcriptional bubble

50
Q

What is RNA chain initiation?

A

First 2 ribonucleotide line up on template strand in the transcription bubble and RNA polymerase catalysed phosphodiester bond formation

51
Q

What is abortive transcription?

A

Formation of short transcripts which are released

52
Q

What is promoter escape?

A

Chain extensions beyond 7 ribonucleotides trigger TFIIB release and formation of transcriptional elongation complex

53
Q

RNA polymerase must be … for elongation?

A

Phosphorylated

54
Q

What is the important role of carboxyl terminal domain (CTD)?

A

Transition from initiation complex to elongation complex

55
Q

How many subunits do TFIIH have?

A

10

56
Q

What is the structure of TFIIH?

A

10’subunits, ring shaped 5’—>3’ and 3’ —> 5’ helicase activities Cyclin dependent protein kinase activation

57
Q

What does ser-5 phosphorylation of RNA pol II permit ?

A

Promoter clearance

58
Q

What are phosphorylated in RNA polymerase II during elongation?

A

Ser-2 and Ser-7

59
Q

What is more stable than initiation complex?

A

Elongation complex

60
Q

How many base pairs are melted to form the transcription bubble ?

A

14bp

61
Q

How many nucleotides within bubble are paired with RNA chain?

A

First 8 nucleotides

62
Q

Where does the transcription bubble extend from?

A

-12 to +2

63
Q

What is phosphorylation of CTD involved in?

A

Processing MRNA transcript

64
Q

What does phosphorylation of CTD provide ?

A

Binding/recognition sites for mRNA processing

65
Q

Does RNA polymerase have a steady pace ?

A

No

66
Q

What happens to chain elongation at pause sites?

A

Temporarily delayed

67
Q

What May pausing of chain elongation cause?

A

Pausing may lead to arrest and termination arrests is an important step in proof reading

68
Q

What re-activates arrested RNA polymerase II?

A

TFIIS

69
Q

What form of promoter is RNA polymerase I?

A

Bipartile promoter

70
Q

What does RNA polymerase I consist of?

A

Upstream promoter element (UPE) Core binding factor SL1

71
Q

What does the factor UBF1 do?

A

Wrap DNA around a protein structure to bring the core and UPE into proximity

72
Q

What does SL1 Include?

A

TATA binding protein that is involved in the initiation by all three polymerases

73
Q

RNA polymerase I binds to what at core promoter?

A

UBF1-SL1

74
Q

What does RNA polymerase III use?

A

Downstream and upstream promoters

75
Q

How many types of promoters does RNA polymerase III have?

A

3

76
Q

How many internal promoters does RNA polymerase III?

A

2

77
Q

What are internal promoters?

A

Have short consensus sequences located within transcription unit and cause Initiation to occur at a fixed distance upstream

78
Q

What are upstream promoters?

A

Contain 3 short consensus sequences upstream of the start point that are bound by transcription factors TFIIIA and TFIIIC bind to the consensus sequences and enables TFIIIB to bind at start point

Human Molecular B (13 decks)

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