Alternative splicing of a
tropomyosin
There are 3 forms of
polypyrimiding tract binding protein (PTB) PTB1, PTB2 and PTB4.
Binding of PTB4 to the
polypyrimidine suppresses splicing while binding of PTB1
promotes splicing. In smooth muscle exon 3 of a-tropomyosin
is not present. Thus,
PTB4 is expressed in smooth muscle
while PTB1 is not.