BAG-1 INHIBITS P53-INDUCED BUT NOT APOPTIN-INDUCED APOPTOSIS

BAG-1 has been identified as a Bet-a-binding protein that inhibits apo ptosis, either alone or in co-operation with Bcl-2. Here we show that BAG-1 inhibits p53-induced apoptosis in the human tumour cell line Sao s-2. In contrast, BAG-1 was unable to inhibit the p53-independent path way induced by apoptin, an apoptosis-inducing protein derived from chi cken anaemia virus. Whereas BAG-1 seemed to co-operate with Bcl-2 to r epress p53-induced apoptosis, co-expression of these proteins had no i nhibitory effect on apoptin-induced apoptosis. Moreover, Bcl-2, and to some extent also BAG-1, paradoxically enhanced the apoptotic activity of apoptin. These results demonstrate that p53 and apoptin induce apo ptosis through independent pathways, which are differentially regulate d by BAG-1 and Bcl-2.