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BIOL 3321 - cell and molecular bio > post-transcriptional gene control > Flashcards

post-transcriptional gene control Flashcards

1
Q

list the forms of post transcriptional gene control

A

RNA processing, RNA transport out of the nucleus, RNA degradation, and translation

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2
Q

what are riboswitches

A

short sequences of RNA

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3
Q

where are riboswitches located on the RNA strand

A

near the 5’ end

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4
Q

which organism are riboswitches common in

A

bacteria

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5
Q

what do riboswitches do for gene control

A

they regulate the activity of RNA pol via conformational changes

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6
Q

in bacteria, which amino acid are riboswitches used to control the biosynthesis of

A

guanine

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7
Q

describe riboswitches controlling purine synthesis

A

one conformation aids in elongation

another conformation, when guanine is bound to it, RN pol doesn’t transcribe = no purine

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8
Q

what is splicing

A

a process in which the introns are removed from pre-mRNA

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9
Q

what carries out splicing

A

5 small nuclear RNAs (snRNAs) + associated proteins

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10
Q

what are the 5 snRNAs that carry out splicing

A

U1, U2, U4, U5, U6

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11
Q

what do each snRNA and its associated proteins form

A

a small nuclear ribonucleoprotein particle (snRNP)

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12
Q

what is an snRNP

A

a snRNA + its associated proteins

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13
Q

what is a spliceosome

A

the structure formed when all the snRNPs and splicing factors are assembled on the pre-mRNA

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14
Q

what are the 3 consensus sequences around splice sites in pre-mRNAs

A

5’ GU, 3’ AG, and the A branch point in the middle

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15
Q

what is the GU-AG rule

A

the 5’ GU and the 3’ AG are always there

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16
Q

what does the mRNA form when the introns are removed

A

a lariat

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17
Q

what do SR proteins do

A

they bind to exons and help define splice sites

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18
Q

what snRNAs do SR proteins recruit to splice sites

A

U1 and U2

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19
Q

what do hnRNPs do

A

they bond to introns to help the spliceosome

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20
Q

list all the proteins involved in splicing

A

snRNP (snRNA + proteins), SR proteins, hnRNPs

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21
Q

T or F: an RNA transcript can be spliced in more than one way

A

true

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22
Q

what is it called when a transcript can be spliced in more than one way

A

alternative splicing

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23
Q

what is the purpose of alternative splicing

A

allows one gene to produce several related proteins

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24
Q

how many genes are in the human genome

A

~21,000

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25
how many proteins can humans make due to alternative splicing
more than 70,000
26
T or F: for most human genes, alternative splicing occurs
true
27
what are the two types of RNA splicing regulation
positive control negative control
28
describe positive control of RNA splicing regulation
an activator protein is required in order for an intron to be recognized
29
describe negative control of RNA splicing regulation
a repressor protein can bind to the mRNA and block access of the spliceosome
30
what is the poly(A) site
it's where the RNA transcript is cleaved and where the adenines are added to form the 3' tail
31
where is the poly(A) site
at the end of the coding sequence for a gene
32
what is the first step of pre-mRNA processing
after transcription, the 5' cap is added
33
after the 5' cap is added to the transcript, what happens
cleavage at the poly(A) site occurs
34
what enzyme cleaves at the poly(A) site of the pre-mRNA transcript
an endonuclease
35
after cleavage at the poly(A) site, what occurs
polyadenylation occurs at the 3' site
36
how many adenines are added in polyadenylation
~250
37
what enzyme is responsible for polyadenylation
Poly(A) polymerase (PAP)
38
what occurs after polyadenylation
RNA splicing, leaving us with a mature mRNA
39
describe a mature mRNA
has a 5' cap, has been cleaved at the poly(A) site, has a 3' poly A tail, and has introns removed
40
what is the recognition sequence for polyadenylation
AAUAAA
41
what is AAUAAA
the polyadenylation recognition sequence
42
what is another name for AAUAAA
the Poly(A) signal
43
where is the poly(A) signal located
15-30bp upstream from the poly(A) site
44
other than the poly(A) signal, what is an important region during polyadenylation
the GU-rich or U-rich region
45
where is the GU-rich/U-rich region located
~20bp downstream from the cleavage site
46
what thing recognized the poly(A) signal (AAUAAA)
CPSF
47
full name of CPSF?
cleavage and polyadenylation specificity factor
48
what thing recognizes the GU-rich/U-rich signal
CstF
49
full name of CstF?
cleavage stimulation factor
50
where are CPSF and CstF found
on the CTD region of RNA pol
51
starting at CPSF and CstF, describe the mechanism of polyadenylation
CPSF and CstF transfer from CTD to mRNA recognition sequences, and then additional factors (including PAP) bind. PAP binding = cleavage at poly(A) site, PAP adds A's
52
after all the As are added to the transcript, what type of protein binds
poly(A) binding proteins (PABPs)
53
role of poly(A) binding proteins?
helps with export of the mRNA out of the nucleus and it protects mRNA from being degraded by exonucleases
54
T or F: there may be alternative poly(A) sites
true
55
what is the result of having alternative poly(A) sites
results in the productions of proteins that vary at their C terminus
56
what percentage of human genes coding for proteins have more than 1 poly(A) site
~50%
57
what factors influence which poly(A) site is used when there are multiple ones
the type of cell, concentration of CPSFs and CstFs, the sequence of the polyA signal (high or low affinity), presence of RNA binding proteins that either inhibit/enhance the binding of needed factors for polyadenylation
58
what is the concentration of CstF in a resting B cell + what type of transcript is produced + where will the protein be located
low CstF, so it only recognizes a strong affinity site = longer transcript produced. This codes for hydrophobic amino acids = membrane bound protein made
59
what is the concentration of CstF in an active B cell + what type of transcript is produced + where will the protein be located
CstF = high so it recognizes the weak affinity site = shorter mRNA produced = no hydrophobic region = protein is secreted and not membrane bound
60
what are the two types of RNA editing
A to I C to U
61
when will RNA editing affect the protein produced
only when the edits lead to changes within coding regions
62
why does RNA editing occur
originated as a defense against viruses
63
what two things can RNA editing lead to
a change in the amino acid sequence of the protein or a truncated protein
64
what enzyme carried out A to I edits
ADARs
65
describe what occurs that leads to A to I editing
complimentary bases in an intron pair up, making a double stranded RNA. This attracts ADAR which makes the edit
66
what is the C to U edit important for
production of two variants of apolipoprotein
67
describe the C to U edit using the apolipoprotein as an example
in liver, no editing occurs because the enzymes for editing aren't expressed = full length protein produced in the intestines, the edit happens = stop codon made = truncated protein produced

BIOL 3321 - cell and molecular bio (19 decks)

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