Splicing Flashcards
What is splicing?
Removal of introns (non-coding) from RNA and rejoining of exons (coding)
What does splicing involve?
Enzymatic machinery in the cell which recognises specific sequences present in RNA at the cleavage sites
What is a spliceosome?
Large RNA-protein complex that mediates splicing
Have 5 types of snRNA and more than 50 proteins
What is alternative splicing?
Generation of multiple versions (isoforms) of a protein, specific for individual tissues or specific stage of development
What happens in a spliceosome?
snRNA molecules associate with molecule to form snRNP particles
Specificity depends on RNA- snRNA molecules
Once a splice donor site is recognised, the spliceosome scans the DNA sequence until it meets the next splice acceptor site
What are the 5 types of snRNA?
U1: splice odnor
U2: branch sites
U4, 5, 6: bind to cause looping out of the intronic RNA
U5: binds simultaneously to both splice donor and splice acceptor sites
What is the GT-AG rule?
RNA splicing sites are most often flanked by GT bases at 5’ end and AG bases at the 3’ end
What is the role of ncRNA?
Normal biological processes: gene expression, chromatin architecture, transcription, RNA splicing, editing, translation and turnover
Can ncRNA play a role in disease?
Yes. Cancers,neurological conditions, heart conditions
snoRNA- has been shown to control splicing of serotonin receptor 2C also
What is the role of long ncRNA?
Recurit chromatin regulators to specific regions of the genome and thereby modify gene expression
What is the role of small ncRNAs?
snRNA: splicing
snoRNA: modification of rRNAs
microRNA: fine tune the levels of target messenger RNA
What is the role of microRNA? (miRNA)
Suppress translation via non perfect pairing with target mRNA (6-8 nucleotides)
What is the role of siRNA?
Degradation of target RNAs by the RISC- RNAi phenomenon
How many of human protein genes are regulated by miRNAs?
1/3
Where do miRNas come from?
Introns and exons
