Post Transcriptional Gene Control Flashcards
What protective modifications are added to Pre-mRNA before being exported to the nucleus to be translated?
- Capped (5’ Cap)
- Splicing (Splicing of Introns)
- Polyadentlyated (Poly-A Tail_
- Associated with the RNPs in the nucleus
Describe the act of splicing in pre-mRNA.
A large ribonucleoprotien splice some complex catalyzes the joining ig two exons and the removal of introns.
What is responsible for correctly specifying splice sites?
A network of interactions between SR proteins, snRNPs, and spiffy factors to form a cross-section recognition complex.
List the order in which pre-mRNA is processed in eukaryotes after transcription.
- 5’ Capping
- Cleavage at the poly(A) site
- Polyadenylation
- RNA splicing
List two alternative methods of splicing of mRNA
- Sex determination in Drosphilia
- Alternative splicing in neurone of vertebrates
Alternative promoters, alternative splicing, and alternative cleavage at different poly(A) sites yield ______ mRNA from the same gene in different cell types or developmental stages.
Different
_______ are binding to specific sequences near splice sites and regulate alternative splicing.
RNA-binding proteins
Sex-lethal, Tra and Dsx regulate ________ in flies (drosophila).
Sexual differentiation
What is Sxl? Is it a repressor or activator of splicing?
RNA binding proteins that acts as a repressor of splicing.
What is Tra? Is it a repressor or activator of splicing?
RNA binding proton that acts as an activator of splicing.
What is the role of Dsx in Drosphilia?
Transcription activator/repressor.
Sxl controls its own splicing to produce exons ______.
2,4 mRNA.
Males do not include the _____ protein.
Sxl
In males, in the absence of Sxl, the transcripts spliced into exon 2,3,4 mRNA. Where is the stop codon found?
Exon 3 of Sxl
Male or female? sxl - 2,4
Female
Male or female? sxl - 2,3,4
Male -> NOT EXPRESSED
Male or female? tra - 1,3
Female
Male or female? tra -1,2,3
Male - NOT EXPRESSED
Sxl regulates the splicing of the transcript STOP codon in exon ____ of Tra.
Exon 2
Tra regulates __________ and cleavage of Dsx into male and female 2. ________.
- Alternate splicing
- Isoforms
Male or female? Dsx - 3,4
Female
Male or female? Dsx -3,5
Male
Dsx is a ________ binding to DNA with the same DNA binding site in both male and female isoforms.
Transcription factor
The alternative spliced female isofrom of Dsx contains a transcriptional ___________ (activation/repression) domain.
Activation
The alternative spliced male isofrom of Dsx contains a transcriptional ___________ (activation/repression) domain.
Repression
Slx acts as an intron splicing ________ (or inhibitor).
Silencer
Tra acts as an intron splicing _______.
Activator
What is the role of alternative splicing in neurons?
The perception of sounds and neuron connectivity.
miRNA and siRNA regulate the __________ and the ________ of mRNA.
Stability and translation.
siRNA degrade _____ RNA and RNA produced by _________.
Viral, transposons
miRNA IMPERFECTLY bind to the target mRNA. The binding is usually within the 3’-UTR. The imperfect binding leads to _____________.
Repression of translation.
How is siRNA produced?
From cleavage of double stranded RNA
siRNA are produced from the cleavage of _________ DNA
Double stranded
siRNA bind PERFECTLY to the target RNA and cause what?
Rapid degradation by a mechanism called RNA interference. RNA interference controls multiple processes.
Abnormalities in particular miRNA levels play a role in the development of diseases including ______.
Cancer
Explain the function of Drosha.
Remove the hairpins in double stranded RNA.
Describe the function of Exportin.
Transporting the processes miRNA to the cytoplasm.
Describe the function of DICER.
Cuts the double stranded RNA into small pieces.
Describe the function of Argonaut (RISC).
Removes one of the strands of the double stranded RNA and targets the mi
Describe the four steps associated with RNA interference.
- Double stranded RNA is cleaved to small fragments by DICER.
- Small double stranded RNAs bind to RISC and form an inactive complex.
- Argonaut in RISC is an RNA helicase. It unwinds the double stranded RNA and an active RISC* is formed.
- RISC*, guided by single-stranded siRNA, cleaves target mRNA (“SLICER” activity by Argonaut)
What happens with the amplification of RNAi?
