Splicing Flashcards
(20 cards)
What is alternative splicing?
A molecular mechanism that increases the diversity of proteins produced from a limited number of genes
It selectively includes or excludes different exons or introns during mRNA maturation.
What is the role of the spliceosome in alternative splicing?
Mediates the process of alternative splicing
It is a large ribonucleoprotein complex that facilitates the splicing of pre-mRNA.
What are the three key sequence signals recognized during the splicing of pre-mRNA?
- 5’ splice site
- Branch point (A-site)
- 3’ splice site
What is the first step in the mechanism of alternative splicing?
The 2’-OH group of the branch point adenine attacks the phosphate at the 5’ splice site, cleaving the exon-intron junction
This forms a lariat structure.
What happens during the lariat formation in alternative splicing?
A covalent bond is established between the branch point adenine and the intron
Describe the process of exon ligation in alternative splicing.
The free 3’-OH group of the upstream exon attacks the phosphate at the 3’ splice site, joining the two exons
This also releases the lariat structure.
How does alternative splicing differ from constitutive splicing?
Alternative splicing produces multiple mRNA isoforms from the same pre-mRNA, while constitutive splicing results in a single mRNA product
What are some mechanisms of alternative splicing?
- Exon skipping
- Intron retention
- Use of alternative splice sites
What is the commitment complex in spliceosome assembly?
The initial stage where U1-snRNP binds to the 5’ splice site, and other factors interact with the branch point and 3’ splice site
What is the function of U6-snRNP in the spliceosome?
Catalyzes the transesterification reactions that complete the splicing process
Approximately what percentage of human genes undergo alternative splicing?
35%
Why is alternative splicing important for the human proteome?
It allows a genome with about 25,000 genes to produce hundreds of thousands to billions of proteins
What is an example of a gene that undergoes extensive alternative splicing?
The slo gene
This gene regulates potassium ion transport in cochlear hair cells.
What can result from aberrant splicing?
Inclusion of incorrect exons, retention of introns, or creation of cryptic splice sites
What are some causes of aberrant splicing?
- Mutations in pre-mRNA sequences
- Changes in splicing factors
- Transcription-splicing coupling errors
True or False: Aberrant splicing has been implicated in various diseases.
True
How does aberrant splicing contribute to cancer?
It can result in the production of tumor-specific protein isoforms that promote uncontrolled growth and metastasis
What is a consequence of aberrant splicing in neurodegenerative diseases?
Insufficient levels of survival motor neuron protein leading to neuronal loss
Fill in the blank: Alternative splicing provides an efficient mechanism for _______.
[gene economy]
What are the roles of alternative splicing in biological systems?
- Driving proteomic diversity
- Contributing to biological complexity
- Playing crucial roles in development and adaptability
