Inhibition of apoptosis by the African swine fever virus Bcl-2 homologue: Role of the BH1 domain

The function of the African swine fever virus (ASFV)bcl-2homologue, geneA179L,in the regulation of apoptosis was investigated using as a model system the human myeloid leukemia cell line K562 induced to die by apoptosis with inhibitors of macromolecular synthesis, a process that is prevented by overexpression of humanbcl-2.It is shown that transfection of K562 cells with the ASFVA179Lgene protects these cells from apoptotic cell death induced by a combination of cycloheximide and actinomycin D or by treatment with cytosine arabinoside. To test the functional role of the highly conserved BH1 domain present in the A179L protein, the Gly residue at position 85 was mutated to Ala, since it has been shown that substitution of the corresponding Gly in human Bcl-2 abrogates its death-repressor activity. It was found that the Gly-to-Ala mutation in the BH1 domain of the viral protein abolished its capacity to protect the K562 cells from apoptosis, indicating that this Gly is essential for A179L action. This finding stresses the functional similarity of the BH1 domains of the viral protein and cellular Bcl-2.This work was 29. Hockenberry, D. M., Oltvai, Z. N., Yin, X.-M., Milliman, C. L., and supported by grants from the Dirección General de Investigación Korsmeyer, S. J., Cell 75, 241 – 251 (1993). Científica y Técnica (PB93-0160-C02-02), the European Community 30. Nguyen, M., Branton, P. E., Walton, P. A., Oltvai, Z. N., Korsmeyer, (AIR-CT93-1332), and Comunidad de Madrid (AE00424/95), and by an S. J., and Shore, G. C., J. Biol. Chem. 269, 16521 – 16524 (1994). institutional grant from Fundacio´n Ramo´n Areces to the Centro de 31. Afonso, C. L., Neilan, J. G., Kutish, G. F., and Rock, D. L., J. Virol. 70, BiologıBa Molecular ‘‘Severo Ochoa.’