Caspase-mediated cleavage and DNase activity of the translation initiation factor 3, subunit G (eIF3g).

Eukaryotic translation initiation factor 3 is composed of 13 subunits (eIF3a through eIF3m) and plays an essential role in translation. During apoptosis, several caspases rapidly down-regulate protein synthesis by cleaving eIF4G, -4B, -3j, and -2α. In this study, we found that the activation of caspases by cisplatin in T24 cells induces the cleavage of subunit G of the eIF3 complex (eIF3g). The cleavage site (SLRD(220)G) was identified, and we found that the cleaved N-terminus was translocated to the nucleus, activating caspase-3, and that it also showed a strong DNase activity. These data demonstrate the important roles of eIF3g in the translation initiation machinery and in DNA degradation during apoptosis.