PRESENCE OF THE LONG AND SHORT FORMS OF B CL-X IN SEVERAL HUMAN AND MURINE TISSUES

Bcl-X protein, which is related to Bcl-2, is present essentially in th e nervous system and the immune system, under 2 different forms: Bcl-X (L), like Bcl-2, is able to prevent apoptotic death of cultured lympho cytes; in contrast Bcl-X(S) which differs from om the former one by a deletion of 63 amino acids in the region of greatest homology between Bcl-X(L) and Bcl-2, is unable to prevent this apoptotic death and even counteracts the protective effect of Bcl-2. It has been reported that the adult nervous system contains exclusively the RNA encoding Bcl-X( L) whereas the immune system would contain exclusively the RNA encodin g Bcl-X(S). We show here, by using reverse transcription coupled to PC R, that adult rat brain contains not only the RNA encoding Bcl-X(L) bu t also the RNA encoding Bcl-X(S). Similarly we shaw that human lymphoc ytes, whether infected or nat by the HIV contain both forms of Bcl-X m essenger RNA (mRNA). Furthermore we have observed that both forms of m RNA are present in adult rat liver and in cultured mouse hepatocytes. All these results have been confirmed by hybridizing the PCR products transferred to a nylon membrane with a probe specific of Bcl-X(L) or a non discriminative probe.