McNary High School
RNA splicing does not always cut out the same introns or keep the same
exons. If different exons are used to make the mRNA, a different protein will
result. Using exons in this way is called alternative RNA splicing or
alternative splicing. . .
. . . Alternative splicing also occurs in the Survival
of Motor Neuron (SMN1) gene which primarily produces the protein FL-SMN which is
used to assemble components that make up the spliceosome (Meister et al. 2001).
When the alternatively spliced variant is produced, intron 3 becomes an exon and
shortens the protein overall as intron 3 contains a stop codon (Setola et al.
2007). This protein is called axonal SMN (a-SMN) and it appears to stimulate
axon outgrowth and cell motility (Locatelli et al. 2012). Unlike the CARD8
isoforms, these isoforms act on completely different cell functions which shows
the great variety of proteins that can be created by alternative RNA splicing.