Spontaneous fragmentation of several proteins in Drosophila pupae.

Autoproteolysis is an essential activity in the expression of the entire genomes of a number of viruses. That is, new viruses can be produced only after large polyprotein products translated from the genome or from subgenomic mRNA degrade themselves to the polypeptides necessary for RNA replication or for the construction of new virus particles. We have recently shown that the major heat shock protein of Drosophila and a mouse cell line (70 kDa) also undergoes autoproteolysis with the production of specific patterns of smaller polypeptides. We show now that many other proteins in eucaryotic tissues also have a potential for self-degradation. We suggest that special coding regions in many genes may have important roles in both protein turnover and in the production of regulatory peptides.