ATG5 is an E2 ubiquitin ligase which is necessary for autophagy. Its expression is a relatively late event in the apoptotic process, occurring downstream of caspase activity, dramatically highly expressed in apoptotic cells. It is activated by ATG7, conjugates to ATG12 and associates with isolation membrane to form cup-shaped isolation membrane and autophagosome. The conjugate complex detaches from the membrane immediately before or after autophagosome formation is completed. ATG5 plays an important role in the apoptotic process, possibly within the modified cytoskeleton.