Internal deletion causing gain of function?

[Bob Obar]

I'm not sure if this quite fulfills your criteria, but expression of
the mammalian MAP 2 gene produces either a ca. 210 kDa protein (MAP 
2A or MAP 2B) or a 70 kDa protein (MAP 2 C) which is "missing" the 
middle 140 kDa of the larger coding sequence.  These are all made 
from the same gene, but differentially spliced. 

Bob Obar