Please answer all th questions Splicing of mRNA Transcript o Define the terms “i
ID: 196638 • Letter: P
Question
Please answer all th questions
Splicing of mRNA Transcript o Define the terms “intron” and “exon.”
o What are the components of snRNPs?
o What is the spliceosome?
o Where is the spliceosome bound during the process of transcription?
o Describe the splicing reaction catalyzed by the spliceosome. Be sure to mention the: Function of the various snRNPs involved and what constitutes an active spliceosome. The chemical reactions occurring at the branch point, the 5’-end of the splice site, and the 3’-end of the splice site.
• Differential RNA Processing o Describe how the process of alternative cleavage and polyadenylation can lead to proteins with similar but different functionalities.
o Describe how the process of alternative splicing can lead to proteins with similar but different functionalities.
Explain how the alternative splicing of proteins is controlled in eukaryotes.
Explanation / Answer
Answer:
1. a. Introns are long segments of nucleotides that have no coding information.
Exons are portions of a gene that are translated into proteins.
b. snRNPs form the core of the spliceosome and are composed of small nuclear RNAs (snRNAs) and proteins. The snRNPs are identified by which snRNA (U1, U2, U3, U4, U5 and U6) each contains.
c. A spliceosome is a large assembly of RNA and protein molecules that is responsible for carrying out RNA splicing within the cell.
d. snRNPs bind to sites in a pre-mRNA at or near the intron-exon boundaries. These sites are called consensus sequences, and contain nucleotide squences that are shared by most pre-mRNAs. The snRNPs contain RNA molecules that can bind through complementary base paring to the consensus sequences.
The snRNPs eventually come together into a large complex called a spliceosome, as the splicesome forms the intron loops out.
e. The steps of RNA splicing involves:
i. U1 snRNP binds to 5’ splice site, BBP to branchpoint, splicing protein U2AF65 to polypyrimidine tract and U2AF35 to 3’ splice site
ii. U2 snRNP binds branchpoint and displaces BBP (branch point binding protein)
iii. U4/U6.U5 tri-snRNP associates with complex bringing 3’ and 5’ ends of intron close together, U2AF65/35 are released
iv. U1 snRNP is released from complex
v. Reorganization of interactions among snRNPs and release of U4 snRNP from complex
vi. First transesterification reaction which generates branched intron still attached to downstream exon and the freed upstream exon (with its 3’OH nucleophile)
vii. Second transesterification reaction to join exons and release intron as lariat
(Since there are multiple questions, the first full question have been answered according to the rules of Chegg)