Post Transcriptional Control of expression of RNAi Flashcards
How does RNA differ from DNA?
rna less stable than dna
dna is information storage
rna single stranded
rna forms variety of 3d shapes
rna variety of functions
rna more transient
What happens in eukaryotic pre-mRNA processing?
Splicing
removal of introns
creates mature mRNA
5- cap added
poly A tail on 3’
What is an open reading frame?
stretch of codons that start with a start codon and end with a stop codon
transcript then translated into a protein
Splicing
exons are not scrambled
different exons included or excluded dependent on gene
creates different protein isoforms
can occur in tissue specific manner
how is alternative splicing regulated?
according to tissue type
multiple different splicing variants within a cell
by activators and repressors
- mask binding site or encourage binding
negative control = repressor and no splicing
positive control = activator and splicing
What is RNA editing?
common in parasites
mature mRNA doesn’t correspond to DNA sequence
addition or deletion of uridine to mRNA
deamination of A to give I
deamination of C to give U
How do UTRs control mRNA stability?
protein sits in cell membrane and involved in uptake
regions in 3’ untranslated region; combine to iron response protein
changes shape, mRNA degraded
can also affect levels of translation
What is RNAi?
mediates resistance to parasitic and pathogenic nucleic acids
regulates expression of protein-coding genes
involved in gene silencing
How does RNAi gene silencing work?
- double stranded RNA chopped up & small pieces associated with protein
- one strand strips away & base pair by complementary base pairing
just replacing the one strand with th eRNAi by complementary gene pairing
What are miRNAs?
regulate gene expression by blocking translation of specific mRNAs
cause their degradation
How do mRNAis work?
Transcribed by RNA polymerase 2
1. crop off the ends on the nucleus
2. cleave the loop in the cytoplasm
3. one strand is also degraded
4. RISC matches and then alters expression
Why is miRNA regulation important?
involved in fine tuning of genes
key regulators in many biological processes
What is gene knockdown?
useful in the labs
can add miRNA to an organism & target specfic genes to reduce them
How can RNAi be used as a tool to control infectious disease?
By oral administration
potential use of dsRNA to control viral diseases in farmed shrimp
through intramuscular administration
How can RNA be used in medicine?
to treat transthyretin-mdeiated amyloidosis
