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Molecular Biology > Ch. 17c RNA Processing & Transcription Regulation (Exam 2) > Flashcards

Ch. 17c RNA Processing & Transcription Regulation (Exam 2) Flashcards

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1
Q

What does post-transcriptional gene control mean?

A

All processes regulating gene expression after the start of transcription

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2
Q

What are the 3 main processes of pre-mRNA processing?

A

1) 5’ capping
2) Polyadenylation
3) Intron splicing

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3
Q

What is a 5’ cap?

A

Modification of the 5’ on the primary transcript (pre-mRNA)

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4
Q

What does a 5’ cap create?

A

7-methylguanylate (m7Gppp) attached to the first nucleotide of the pre-mRNA

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5
Q

How does m7Gppp link to the first nucleotide of pre-mRNA?

A

5’-5’ linkage that links the 5’C of one pentose to another

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6
Q

What are 3 purposes of the 5’ cap?

A

1) Transport of mRNA to cytoplasm
2) Protect against nuclease
3) Start translation

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7
Q

M7Gppp is an example of a…

A

Nucleoside triphosphate

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8
Q

What 4 things does the 5’ cap structure influence in mRNA?

A

1) Stability
2) Splicing
3) Export
4) Translation

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9
Q

Pre-mRNA is the primary transcript with the same organization as…

A

The gene

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10
Q

What is splicing?

A

Removal of introns to turn pre-mRNA into mature mRNA

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11
Q

What is the purpose of the pre-mRNA splice sites?

A

To help direct splicing reactions

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12
Q

Where is the 5’ splice site?

A

On the 5’, left end of the intron

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13
Q

What consensus sequence does the 5’ splice site include (HINT: 2 nucleotide bases)?

A

GU

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14
Q

Where is the 3’ splice site?

A

On the 3’, left end of the intron

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15
Q

What consensus sequence does the 3’ splice site include?

A

AG

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16
Q

Is the central region of the intron important for splicing?

A

Generally, no

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17
Q

What does the GU-AG rule describe?

A

The requirement of these dinucleotides at the 5’ and 3’ splice sites respectively so that they come together after splicing

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18
Q

What 3 things does splicing require?

A

1) 5’ splice site
2) 3’ splice site
3) Branch site

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19
Q

What is the purpose of the branch site?

A

To initiate a nucleophilic attack on the 5’ splice site

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20
Q

Splicing requires 2 { } reactions.

A

Transesterification

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21
Q

What happens in the first transesterification reaction?

A

Nucleophilic attack from branch site OH group cleaves phosphodiester bond at 5’ splice site

22
Q

What happens in the second transesterification reaction?

A

3’ OH group of 5’ exon does nucleophilic attack at the 3’ splice site

23
Q

What is the major product of transesterification?

A

Spliced exons

24
Q

What is the minor product of transesterification?

A

Lariat product

25
Q

What does the lariat product consist of?

A

Excised intron

26
Q

What does the acronym snRNA stand for?

A

Small nuclear RNA

27
Q

How many snRNAs does splicing require? What are they?

A

5; U1, U2, U4, U5, U6

28
Q

What does the acronym snRNP stand for?

A

Small nuclear ribonucleoprotein particles

29
Q

What is a spliceosome?

A

Complex of all 5 snRNAs and pre-mRNA

30
Q

What does the complex on the pre-mRNA intron consist of?

A

1) U1 on 5’ splice site
2) SF1 & U2AF on branch point A
3) 3’ AG dinucleotide

31
Q

What is the first step of splicing with the spliceosome complex?

A

Splicing factor 1 (SF1) moves out, and U2 is added in

32
Q

After the U2 snRNP is added to the pre-mRNA, what happens in the second step of splicing?

A

U4-6 are added on to fully form the spliceosome

33
Q

After the spliceosome fully forms, what is the third step of splicing?

A

U1 & 4 move out, and the pre-mRNA gets ready for splicing

34
Q

After U1 & U4 are gone from the pre-mRNA, what are the 4th and 5th steps of splicing?

A

Transesterification

35
Q

After transesterification, what is the 6th step of splicing?

A

Debranching w/ debranching enzyme to cleave 2’-5’ branch point

36
Q

What is the point of cleaving the 2’-5’ branch point?

A

Expelling the lariat

37
Q

What are the 2 purposes of the poly(A) tail after 3’ cleavage and polyadenylation?

A

Nuclear transport & translation

38
Q

How is eukaryotic gene expression controlled?

A

Initiating transcription by opening up the chromatin

39
Q

On what 3 occasions/circumstances will mRNA be regulated?

A

1) Transportation to the cytoplasm
2) Translation
3) Degradation

40
Q

Controlling eukaryotic gene expression determines which form of a { } is represented in mRNA.

A

Gene

41
Q

This chemical reaction, which involves the introduction of an acetyl group, is associated with gene activation…

A

Acetylation

42
Q

What is the relationship between transcription factor concentration, chromatin condensation, & transcription?

A

Higher concentration = less condensation = open for transcription

43
Q

In acetylation, acetyl groups are added to the positively-charged side chain of this amino acid…

A

Lysine

44
Q

Are acetyl groups added to the C-terminal or N-terminal of the core histone?

A

N-terminal

45
Q

What is the relationship between histone binding strength and transcription activity?

A

Weaker histone binding = greater transcription activity

46
Q

What are nucleosome remodeling factors?

A

Protein complexes that facilitate the binding of transcription factors by altering nucleosome structures

47
Q

What is the mechanism of action of nucleosome remodeling factors?

A

Science isn’t sure yet, but these factors appear to allow proteins easier access to nucleosomal DNA without removing histones

48
Q

What hypothesis may answer how the nucleosome remodeling factors help transcription factor binding (HINT: they catalyze something)?

A

They catalyze the sliding of histone octamers along DNA

49
Q

How does DNA methylation control transcription?

A

Methylation reduces transcription activity, which means that the chromatin are more condensed

50
Q

How does protein MeCP2 function?

A

It works with histone deacetylase, which alters nucleosome structure, and inhibits transcription activity i.e. it’s a gene repressor

Molecular Biology (21 decks)

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