Regulation Of Transcription 2 Flashcards
What is rna editing
Alteration or modification of nucleotides in rna
What rna goes through editing
Mrna tRNA and rRNA
Which disease is caused by editing
Atherosclerosis
How can editing affect the brain
High functioning things like depression
How does editing allow parasites to be drug targets
Via U insertion in their mt
Give 2 examples of methylation editing
M5cytosine - cytosine at n 5 is methylated irreversibly
M6adenine - methylated at 6’
How does editing affect action of uridine which binds to adenine
It is converted to pseudouridine via an isomerisation reaction
Produces an extra H bond
What is better about pseudouridine edited from uridine
It has extra h bond potential which increases rna stability
Bases can be fully changed in identity aswell as altered. What are the 2 ways
A deamination to I (inosine)(recognised as G)
C to U deamination (loss of NH2)
How can U insertion or U from c deamination affect mrna
Can cause introduction of a start AUG codon or a stop UAA/UAG codon
How does editing such as change in bases affect splicing
Can change splice sites
Can editing cause change in AA sequence
Yes Eg via insertion/deletion or alteration via deamination
Does M6A methylation affect base pairing of A with U
No
How can m6a affect rna
Methylation can either stimulate protein binding. Proteins which improve rna stability
Or
It can block then causing instability and degradation
Which eraser of the m6a is involved in obesity
FTP
Other than protein binding what does m6a affect
Splicing, export and translation
How does cytidine deamination to U affect apo B gene in intestines
In intestines the c is deaminated to U in the apoB gene introducing a new stop codon. The protein is much shorter forming apob48 and without an LDL receptor
Does cytidine deamination into U occur in liver apoB gene
No. There is no stop codon and so long protein apoB 100 is produced with an LDL receptor intact
Which enzyme deaminates A to I
Adar 2
How has A deamination to I via adar 2 affected transmission of glutamate Nt across synapse
Changed amino acid in transporter from Q glutamine to R arginine. This transporter is now not permeable to calcium = no transmission
How is ribose modified in trna, snrna and rRNA
2’ O methylation of ribose
How does ribose 2’ o methylation affect things in trna rRNA and snrna
Changes stability by blocking nucleases
Also changes protein binding
What happens to yeast if there’s no rRNA 2’ o methylation on ribose
They die
What Happens to yeast if the pseudouridine from isomerisation of uridine in rRNA is removed
Defect in translation as it needs rRNA stability
Which enzyme is mutated which modifies rRNA in dyskeratosis congenita
Pseudouridine synthase
Does editing also occur on non coding rna
Yes Eg sn rna 2’ o methylation
Explain the structure of nuclear pores
Nucleoplasm and cytoplasm are separated by the outer and inner nuclear membrane
There is a nuclear basket and on the cytoplasmic side there are long cytoplasmic filaments
What 2 things are needed for exportation
Export factors and export adapters
What do export adapters do
Couple processes like capping, poly A which have export factors with mrna to export receptors/factors
What is an important thing in exportation for energy
Ran gtp
Which export factors carries trna
Exp-t
Which export factor carries mirna
Exp-5
Which rnas need export adapters to attach to them and connect them to export receptors
Snrna,mrna and rRNA
Which export adapter is the main one in mrna exportation
ALY/yra1
What are the 2 human export factors for mrna (attach to ALY/yra1)
TAP and p15
What is rna localisation described as
Asymmetric
What is importance of rna localisation being asymmetrical
Localised protein synthesis
Generates cell polarity in development
Prevents expression of genes I. Wrong place
Give an example of cell polarity via asymmetrical mrna localisation
Bcd bicoid mrna localised on edge of oocyte to form the APVD axis
When proteins are translated they form a gradient forming the axis
Give an example of localised translation of mrna = prevents expression In wrong place
NTs mrna is translated at the synapse after travelling down dendrites
Which 2 modes of transport do mrna localise through
Diffusion and active transport
Which proteins hold and localise mrna after diffusion localisation
Anchor proteins
Give an example of active transport localisation
Mrna moves down dendrite via AT anchored to the cytoskeleton
What state is mrna in until right localisation
Inactive state so no translation occurs
