RR9 Flashcards
What are the two trans-esterifications in intron splicing?
1) Cutting at 5’ end of intron COH group attacked 5’ phosphate
2) Cutting at 3’ end of intron, exon I attacks section of exon still attached.
When does rRNA cleave?
It only cleaves when transcription is terminated. 18s, 5.8s and 28s are always transcribed in the same sequence.
How are pre-tRNAs modified?
They are transcribed by RNA Pol II.
1) 5’ sequence is removed
2) Short segment is removed
3) CCA is added on 3’ end
4) there is extensive modification of internal bases
What is RRM?
RNA recognition motif that folds up structure with beta sheets, giving it a positive charge.
RNA-recognition motif (RRM) is an RNA-interacting protein domain that plays an important role in the processes of RNA metabolism such as the splicing, editing, export, degradation, and regulation of translation.
What is PTB?
Small RNA binding molecule that aids in splicing.
What is U2AF?
Protein component that defines the 3’ splice site; helps with splicing efficiency.
What are SR proteins?
They are RNA binding proteins with RRM domains and protein:protein interaction domains. They aid in binding of splicing sequence to exons (U1SnRNP and U2SnRNP)
What is the cross-exon recognition complex?
SRprotein:Protein/snRNA
What is alternative splicing? What is an example?
This process splices pre-mRNAs in different ways, giving rise to different proteins and allowing higher complexity.
An example is sexual dimorphism in brosophila which is due to alternative splicing. Sx1 is expressed in females, “late” Sxi promoter is in both sexes, it is alternatively splices, only females have it, allowing them to express SxI. Alternative splicing leads to TRA in females. Males have code in exon 3 that will interupt Sxl protein formation. (have 2 3 4.) Females splice exon I and 3, making Tra protein.
What is an example of RNA editing?
Apolipoproteins B - involved in liver and gut, cholesterol.
Are all mRNA polyadenylated?
Not histone mRNAs. mRNAs without poly (A) usually rapidly degrade in nucleus, not histones.
What is polyadenylation?
- Poly A polymerase has 12A residues added to 3’ end. The structure is recognized by PABPI I, which catalyzes addition of around 200 A residues.
