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Biochemistry (Cole) > Lecture 28 Gene Production of Proteins > Flashcards

Lecture 28 Gene Production of Proteins Flashcards

1
Q

How do cells achieve their specialized functions?

A
  • Based upon the expression of specific genes and any subsequent post-translation modifications of the resulting proteins
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2
Q

Translation

A
  • RNA to protein
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3
Q

Transcription

A
  • DNA to RNA
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4
Q

Eukaryotic Protein production

A
  1. Transcription in nucleus
  2. 5’ capping RNA splicing
  3. 3’ polyadenylation
  4. Exported to cytoplasm
  5. Translated into protein
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5
Q

Prokaryote protein production

A
  1. Transcription into mRNA

2. Simultaneous translation into protein

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6
Q

Introns

A
  • are transcribed but not translated
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7
Q

What is different in deoxyribose from ribose?

A

The hydroxyl group on 2’

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8
Q

How many strands of DNA is transcribed into RNA?

A

one

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9
Q

What direction is RNA synthesized?

A

5’ to 3’

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10
Q

What direction is the DNA template strand oriented in?

A

3’ to 5’

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11
Q

Promoters

A
  • sequences in the DNA that promote or direct transcription of a gene
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12
Q

What are most protein coding genes transcribed by?

A
  • RNA polymerase II
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13
Q

Transcription

A
  • initiates at a specific point in the DNA and requires unwinding of the DNA to create the proper single-stranded template
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14
Q

Gene expression regulatory proteins

A
  • recognize specific DNA sequences and upon binding regulate if, when, and to what extent a gene is transcribed.
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15
Q

Can you have multiple RNA polymerase molecules transcribing a gene?

A
  • Yes
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16
Q

mRNA

A
  • messenger RNA

- Translated into proteins

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17
Q

tRNA

A
  • transfer RNA

- Transfer amino acids to the growing peptide chain

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18
Q

rRNA

A
  • ribosomal RNA

- Encodes ribosomal proteins

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19
Q

microRNA

A
  • Block translation of specific mRNAs and thereby regulate gene expression (at post translational level)
  • new
  • Last 10 years
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20
Q

siRNA

A
  • small interfering RNAs

- turn off gene expression by directing the selective degradation of mRNAs.

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21
Q

snoRNA

A
  • small nucleolar RNA

- Process and chemically modify rRNAs

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22
Q

what is the most abundant RNA?

A
  • ribosomal RNA (80%)
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23
Q

Where is the TATA located?

A
  • 25 base pairs upstream or downstream from start cite of transcription
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24
Q

What does TATA box do?

A
  • Phases binding proteins that bring in RNA polymerase so that it starts at the right spot
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25
Q

What binds to TATA box first?

A

TFIID

- has part called TBP that binds it at the right spot

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26
Q

TFIIB

A
  • binds after TFIID
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27
Q

What is required for TFIID and TFIIB to bind?

A
  • must have regulatory transcription factors present for the process to initiate
28
Q

TFIIH

A
  • important transcription factor that has heliocase activity
29
Q

What does phosphorylation of C terminal domain of the RNA polymerase do?

A
  • open the polymerase to an active conformation for transcription
  • some transcription factors will disassemble
30
Q

TFIID

A
  • recognizes the TATA box

- has subunits (TBP)

31
Q

RNA pol I

A
  • transcription of rRNA genes,
32
Q

RNA pol III

A
  • transcribes tRNA genes, 5S rRNA
33
Q

RNA processing

A
  • Capping
  • Splicing
  • Editing
  • Polyadenylation
  • Transport
34
Q

When does splicing take place?

A
  • as transcription is proceeding
35
Q

Where is the cap located?

A
  • 5’ end
36
Q

Where is the Poly A tail located?

A
  • 3’ end
37
Q

Spliceosome

A
  • performs splicing

- made up of snRNAs in complex with 7 protein subunits to form SNP

38
Q

snRNAs involved in splicing

A
  • U1
  • U2
  • U4
  • U5
  • U6
39
Q

What do snRNAs do in splicing?

A
  • provide for proper base pairing with the mRNA

- These RNA-RNA arrangements are dynamic and shift throughout the splicing process

40
Q

When does 5’ capping occur?

A
  • as soon as the hnRNA emerges from the RNA polymerase

- could be before splicing has been done

41
Q

When is the poly A tail added to mRNA and what adds it?

A
  • as soon as it emerges from the RNA polymerase

-

42
Q

What is microRNA?

A
  • small non-coding RNA
  • 21-25 nt in length
  • bind to 3’ UTR region of target to form and RNA-inducing silencing complex
43
Q

What does microRNA do?

A
  • Suppresses protein synthesis and or induce mRNA degradation
  • Each miRNA can target up to 100 different mRNAs
44
Q

codon

A
  • 3 base sequence that codes for one amino acid
45
Q

Important features of the genetic code

A
  • comma-less (read from beginning to end so reading frame is critical)
  • degenerate (more than one codon can make the same amino acid)
  • The third base in the triplet codon is less specific than the first tow
  • 3 of 64 possible codons do not code for amino acids but signal termination
46
Q

AUG

A
  • codes for methyleline and is where translation starts
47
Q

What are the stop codons?

A
  • UAA
  • UAG
  • UGA
48
Q

Where are ribosomes assembles?

A
  • Nucleus (nucleolus)

- Nucleolus is not a membrane bound structure

49
Q

SnoRNAs

A
  • serve as guide RNAs to direct specific modifications of the RNAs
  • These modifications include methylations, and isomerizations
50
Q

Robert syndrome

A
  • mild retardation
  • retardation, craniofacial abnormalities
  • short arms/legs
  • decrease in rRNA leads to decreased protein synthesis
51
Q

Roberts syndrome

A
  • decreased protein synthesis of rRNA genes
  • Homozygous mutation of ESCO2 which encodes an acetyltransferase important for the foramtion of the cohesion complex that binds to chromosomes and creates cohesion between sister chromatids.
52
Q

Free ribosomes

A
  • move anywhere in the cytosol but are not found in the nucleus and other organelles
53
Q

Membrane bound

A
  • if the protein being made contains an ER targeting sequence then the ribosome is associated with the ER in the rough ER
  • These types of proteins are transported to their destination through a secretory pathway and are usually associated with the plasma membrane or secreted out of the cell
54
Q

Translation

A
  • mRNA is read by the ribosomal machine as a triplet of sequential nucleotides (called a codon)
  • Translation starts at the 5’ end of the mRNA
  • tRNAs are “charged” by the addition of a specific amino acid that corresponds to that codon. this aminoacyl-tRNA is created by the action of enzymes called aminoacyl-tRNA synthase
  • Protein translation uses base pairing between the mRNA codon and a triplet complementary sequence in the tRNA called the anticodon
55
Q

Four steps of translation

A
  • Activation
  • Initiation
  • Elongation
  • Termination
56
Q

Activation

A
  • formation of aminoacyl- tRNAs
57
Q

`Initiation

A
  • binding of small ribosomes to 5’ end of mRNA and subsequent binding of initiator Met-tRNA
58
Q

Elongation

A
  • synthesis of the peptide chain
59
Q

Termination

A
  • synthesis stops and peptide (protein) is released from the ribosome
60
Q

What is the initiator of translation?

A
  • Met-tRNA
61
Q

When does translation stop?

A
  • when two stop codons are encountered in the mRNA
62
Q

Many antibiotics target transcription or translation

A
  • rifamycin
  • tetracycline
  • streptomycin
  • chloramphenicol
  • erythromycin
63
Q

Rifamycin

A
  • prevents RNA synthesis
64
Q

Tetracycline

A
  • Blocks binding of the aminoacyl-tRNA to the A-site (also binds to newly forming mineralizing surfaces such as bone and teeth)
  • causes staining
  • don’t use in children bc of staining
65
Q

Streptomycin

A
  • prevents the switch from translation initiation to elongation and also can cause protein miscoding
66
Q

Chloramphenicol

A
  • blocks the peptidyl transferase reaction so elongation is prevented
67
Q

Erythromycin

A
  • blocks the ribosomal exit channel in the ribosome so elongation is inhibition

Biochemistry (Cole) (25 decks)

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