Regulatory RNA Flashcards
What is the mechanism of attenuation in controlling operon gene expression
Attenuation is a regulatory strategy to halt transcription of operon before the entire mRNA is transcribed based on the abundance of tryptophan.
This relies on the formation of 2° RNA structures in the leader sequence of the mRNA.
When tryptophan levels are low ribosome stalls leading to hairpin structures forming and transcription terminating
What are riboswitches
Structured elements found in non coding regions of mRNA that regulate gene expression by binding to specific metabolites.
Commonly found in 5’-UTR of mRNA and exert control in cis format controlling efficiency of initiation and elongation.
How can riboswitches be engineered to control gene expression in response to ligands
By modifying their aptamer domains which are responsible for ligand binding.
You do this by introducing mutations that change it’s sequence and their structure so they can selectively bind to a specific ligand of choice
Also you can alter the 2° structure of the expression platform to control gene expression by affecting accessibility of the ribosome binding site and transcription terminal signals
How do sRNAs interact with and regulate mRNA
Small RNA are found in bacteria and play a role on post transcriptional regulation of gene expression
They interact with mRNAs forming duplex sRNA-mRNA regions repressing the expression of target DNA.
The international are mediated by RNA binding proteins like RNase E and Hfq
How are exons and introns marked in the nucleus
SR proteins mark exons which recruit spliceosome components to the 5’ and 3’ splice site cleaving out the introns
What is alternative splicing
Process allowing a single gene to produce multiple different forms of the genes protein product (isoforms)
This works by selecting different combinations of splice sites to produce variably spliced mRNAs leading to the translation of distinct protein products.
The drosophila gene lining the gut has 38016 different isoforms that can recognise different antigens (acts as immune response)
What is the importance of RNA regulatory systems in mRNA
In 5’-UTR the presence of the 2° structure elements can modulate initiation in translation.
The 3’-UTR contains cos regulatory systems like binding sites for RNA binding proteins and microRNAs which can influence stability.
How does RNAi protect the cell from viruses and transposable elements
RNA interference recognises viral RNA and targets it for cleavage.
It also maintains the transcriptional silence of transposable elements (genomic sequences capable of influencing gene expression which could disrupt the genome)
How does RNAi process work
Initiated by enzyme dicer which cleaves long dsRNA molecules into siRNA (ds)
siRNA is unwounded into ssRNA and the sense strand is cleaved by protein Ago2 and the antisense strand is incorporated into RNA-induced silencing complex.
The antisense RNA base pairs binds to complementary bases in the RISC and degrades the target mRNA leading to suppression in gene expression.
How can RNAi be exploited in gene knock-downs
By introducing siRNAs into the cell which will inhibit gene activity without having to use mutants or knockouts.
