(A) Full length PIDD1 (FL-PIDD1) is processed into three different fragments. Auto-proteolytic cleavage between F445 and S446 produces PIDD1-N (48 kDa) and PIDD1-C (51 kDa). Further cleavage at S588 forms the PIDD1-CC (37 kDa) fragment. (B) Outline of the chemical transitions needed for PIDD1 auto-proteolysis. The same mechanism is supposed to occur to generate PIDD1-C and PIDD1-CC, in a sequential manner (please see main text for further details).