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
2
Q
Translation
A
- RNA to protein
3
Q
Transcription
A
- DNA to RNA
4
Q
Eukaryotic Protein production
A
- Transcription in nucleus
- 5’ capping RNA splicing
- 3’ polyadenylation
- Exported to cytoplasm
- Translated into protein
5
Q
Prokaryote protein production
A
- Transcription into mRNA
2. Simultaneous translation into protein
6
Q
Introns
A
- are transcribed but not translated
7
Q
What is different in deoxyribose from ribose?
A
The hydroxyl group on 2’
8
Q
How many strands of DNA is transcribed into RNA?
A
one
9
Q
What direction is RNA synthesized?
A
5’ to 3’
10
Q
What direction is the DNA template strand oriented in?
A
3’ to 5’
11
Q
Promoters
A
- sequences in the DNA that promote or direct transcription of a gene
12
Q
What are most protein coding genes transcribed by?
A
- RNA polymerase II
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
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.
15
Q
Can you have multiple RNA polymerase molecules transcribing a gene?
A
- Yes
16
Q
mRNA
A
- messenger RNA
- Translated into proteins
17
Q
tRNA
A
- transfer RNA
- Transfer amino acids to the growing peptide chain
18
Q
rRNA
A
- ribosomal RNA
- Encodes ribosomal proteins
19
Q
microRNA
A
- Block translation of specific mRNAs and thereby regulate gene expression (at post translational level)
- new
- Last 10 years
20
Q
siRNA
A
- small interfering RNAs
- turn off gene expression by directing the selective degradation of mRNAs.
21
Q
snoRNA
A
- small nucleolar RNA
- Process and chemically modify rRNAs
22
Q
what is the most abundant RNA?
A
- ribosomal RNA (80%)
23
Q
Where is the TATA located?
A
- 25 base pairs upstream or downstream from start cite of transcription
24
Q
What does TATA box do?
A
- Phases binding proteins that bring in RNA polymerase so that it starts at the right spot
25
What binds to TATA box first?
TFIID
| - has part called TBP that binds it at the right spot
26
TFIIB
- binds after TFIID
27
What is required for TFIID and TFIIB to bind?
- must have regulatory transcription factors present for the process to initiate
28
TFIIH
- important transcription factor that has heliocase activity
29
What does phosphorylation of C terminal domain of the RNA polymerase do?
- open the polymerase to an active conformation for transcription
- some transcription factors will disassemble
30
TFIID
- recognizes the TATA box
| - has subunits (TBP)
31
RNA pol I
- transcription of rRNA genes,
32
RNA pol III
- transcribes tRNA genes, 5S rRNA
33
RNA processing
- Capping
- Splicing
- Editing
- Polyadenylation
- Transport
34
When does splicing take place?
- as transcription is proceeding
35
Where is the cap located?
- 5' end
36
Where is the Poly A tail located?
- 3' end
37
Spliceosome
- performs splicing
| - made up of snRNAs in complex with 7 protein subunits to form SNP
38
snRNAs involved in splicing
- U1
- U2
- U4
- U5
- U6
39
What do snRNAs do in splicing?
- provide for proper base pairing with the mRNA
| - These RNA-RNA arrangements are dynamic and shift throughout the splicing process
40
When does 5' capping occur?
- as soon as the hnRNA emerges from the RNA polymerase
| - could be before splicing has been done
41
When is the poly A tail added to mRNA and what adds it?
- as soon as it emerges from the RNA polymerase
| -
42
What is microRNA?
- small non-coding RNA
- 21-25 nt in length
- bind to 3' UTR region of target to form and RNA-inducing silencing complex
43
What does microRNA do?
- Suppresses protein synthesis and or induce mRNA degradation
- Each miRNA can target up to 100 different mRNAs
44
codon
- 3 base sequence that codes for one amino acid
45
Important features of the genetic code
- 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
AUG
- codes for methyleline and is where translation starts
47
What are the stop codons?
- UAA
- UAG
- UGA
48
Where are ribosomes assembles?
- Nucleus (nucleolus)
| - Nucleolus is not a membrane bound structure
49
SnoRNAs
- serve as guide RNAs to direct specific modifications of the RNAs
- These modifications include methylations, and isomerizations
50
Robert syndrome
- mild retardation
- retardation, craniofacial abnormalities
- short arms/legs
- decrease in rRNA leads to decreased protein synthesis
51
Roberts syndrome
- 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
Free ribosomes
- move anywhere in the cytosol but are not found in the nucleus and other organelles
53
Membrane bound
- 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
Translation
- 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
Four steps of translation
- Activation
- Initiation
- Elongation
- Termination
56
Activation
- formation of aminoacyl- tRNAs
57
`Initiation
- binding of small ribosomes to 5' end of mRNA and subsequent binding of initiator Met-tRNA
58
Elongation
- synthesis of the peptide chain
59
Termination
- synthesis stops and peptide (protein) is released from the ribosome
60
What is the initiator of translation?
- Met-tRNA
61
When does translation stop?
- when two stop codons are encountered in the mRNA
62
Many antibiotics target transcription or translation
- rifamycin
- tetracycline
- streptomycin
- chloramphenicol
- erythromycin
63
Rifamycin
- prevents RNA synthesis
64
Tetracycline
- 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
Streptomycin
- prevents the switch from translation initiation to elongation and also can cause protein miscoding
66
Chloramphenicol
- blocks the peptidyl transferase reaction so elongation is prevented
67
Erythromycin
- blocks the ribosomal exit channel in the ribosome so elongation is inhibition
