Alternative Splicing & Poly (A) Site Choice; differential RNA processing

Описание: Alternative Splicing & Poly (A) Site Choice: One of the paradoxes of modern genomics is that the apparent complexity of organisms does not correlate with the number of protein coding genes or even the amount of genomic DNA. Some eukaryotic mRNA transcripts can be processed in more than one way to produce different mRNAs and thus different polypeptides.
Two main events are there involved in this;
1) Alternative Splicing: Particular exon may or may not be incorporated into mature mRNA transcript. This leads to formation of different functional mRNA and thus different polypeptides. Primary transcript contains molecular signals for all the alternative processing pathways and the pathway favored in a given cell or metabolic situation is determined by processing factors and RNA binding proteins that promote one particular path.
2) Poly (A) site choice: If there are two or more sites for cleavage and polyadenylation, use of the one closest to the 5’end will remove more of the primary transcript sequence and thus forming smaller functional mRNA. This leads to formation of smaller polypeptide.