Degradation of GST fusion proteins - (Sep/17/2004 )

I clone GST fusion proteins with pGEX 4T-3 vector, I check for inserts in minipreps (OK), grow bacteria, induce them, and run lysates on SDS-PAGE. What happens is that the expressed proteins are of GST size, probably degraded. Has anyone got that kind of results before? I checked DNA, it's OK, no stop codons at the ligation site.