mRNA Translation 1 Flashcards
Prokaryotes vs Eukaryotes main difference in transduction?
Prokaryotes:
No Nucleus
No need for modifications
Eukaryotes:
The RNA cannot be directly translated
It has to first be modified to become mature!
What are the steps of RNA maturation in Eukaryotes?
1- Addition de la coiffe en 5’
2- Épissage des introns
3- Polyadénylation
Outre son rôle dans la transcription, l’ARN polymérase:
recrute via sa queue hyperphosphorylée des protéines impliquées dans la maturation de l’ARN
Capping Enzyme (CE)
Added while transcribing by the RNA polymerase
Addition de la coiffe (cap) par la
Capping Enzyme (CE) à l’extrémité
5’ de l’ARN dès que l’ARN synthétisé
par l’ARN polymérase atteint environ
25 nucléotides de longueur
What kind of binding is the CAP protein? Why is this important
Liaison 5’ vers 5’ inhabituelle au début de l’ARN
résulte en un ARN plus résistant aux nucléases qui digèrent de 5’ vers 3’
What is the function of the cap?
Tells the cells, hey this is an important protein, let’s not destroy it right away
1) Stabilité (protection contre exonucléases du cytoplasme)
2) Facilite l’export de l’ARNm vers le cytoplasme
3) Stimule la traduction par les ribosomes
Explain Recrutement de la Poly-A polymérase (PAP) and fnction.
When the RNA Polymerase reaches the end, it produces a AAUAAA sequence → facteurs de clivage that are on the tail of the RNA polymerase bind to the RNA
This is a signal of cleavage and addition of the polyA tail
This signal leads to the recruitment of Poly-A polymerase (PAP)
PAP can cleave the RNA
ALSO, Ajout de poly-A par la Poly-A polymérase (PAP)
What is the function of the poly A tail?
1) Stabilité (protection contre exonucléases du cytoplasme)
2) Facilite l’export de l’ARNm vers le cytoplasme
3) Stimule la traduction par les ribosomes
How are exons and introns identified?
There are sequences at the exon-intron junction that are VERY VERY specific and conserved → it is key for proper splicing
TRUE OR FALSE,
RNA is unable to perform epissage by itself.
FALSE,
RNA is capable of doing the splicing itself, the proteins are there to assure safe and rapid splicing
What are snRNPs?
Contains RNA and proteins
Binds at the exons and physically brings them together → coordinates splicing and thus removal of introns
assistent la coupure de l’ARN aux jonctions intron-exon et
relient les exons entre eux de façon covalente
What is Epissage alternatif?
Mixing of Exon order and different combinations.
Connect exons that are next to each other, skip exons etc.
This allows for diversity of the gene → instead of 30 000 genes = 30 000 proteins we have billions of proteins
From one GENE we can get multiple proteins
Why is it important for the mRNA to leave the nucleus?
The mRNA must leave the nucleus in order to be translated → THERE ARE NO RIBOSOMES IN THE NUCLEUS, NO WAY TO TRANSLATE
True or False,
If an mRNA is not properly matured it cannot exit the nucleus.
True
Seuls les ARNm maturés correctement peuvent sortir du noyau
Le complexe de pores nucléaires reconnaît et exporte seulement les ARNm qui on terminé leur maturation
