This results in a massive nonspecific release of hydrophilic proteins from the intermembrane space into the cytoplasm. Among these proteins are apoptosis inducing factor and endonuclease G. The release of these proteins results in activation of the apop totic caspases, degradation of nuclear DNA, and currently cell death. However, both AIF and endoG have been found to directly participate in DNA degradation in a caspase inde pendent way. The protein AIF homologous Inhibitors,Modulators,Libraries mitochon drion associated inducer of death, which is probably not located in the mitochondrion, shares sequence homology with AIF and exerts similar apoptotic effects on nuclear chromatin. Interestingly, endoG, AIF and AMID have all been found to influence chromatin changes during apoptosis. EndoG is a mitochondrial nuclease with a molecular weight of 30 kDa.

Its N terminus contains a mitochon drial localization sequence, which is cleaved upon successful transport of the endoG precursor polypeptide across the outer mitochondrial membrane. EndoG Inhibitors,Modulators,Libraries migrates from mitochondria into the nucleus after apop togenic stimuli. Addition of endoG to isolated cell nuclei resulted in cleavage of the chromatin into large fragments and subsequently into inter and intra nucleosomal size fragments with periodically repeated single stranded breaks. The first phase of endoG activity equates with the large scale degradation of DNA during apoptosis, but the second phase would not seem to be able to generate the characteristic laddered fragmen tation of chromatin observed in apoptotic nuclei. This may suggest that endoG normally interacts with other Inhibitors,Modulators,Libraries nucleases.

Indeed, cooperation between endoG, DNase I and exonuclease III has been shown to occur only on iso lated dsDNA. Another proposed interaction partner Inhibitors,Modulators,Libraries for endoG was found by protein analytic in vitro methods to be flap endonuclease 1, but it was not yet shown in living or fixed cells as many other possible interactions mentioned here. AIF is an evolutionary conserved flavoprotein. It shares a high degree of sequence homology with bacterial, plant, and fungal oxi doreductases. The human AIF is expressed as a precursor polypeptide Inhibitors,Modulators,Libraries of molecular weight 67 kDa. This precursor contains an N terminal MLS, which is cleaved, and the active AIF is created in the mitochondrial inter membrane space. AIF is probably bound by its N ter minus to the surface of the inner mitochondrial membrane.

The function of AIF in the mitochon drion under non apoptotic conditions is not clear, but there is evidence that AIF may serve to sequester the free radi cals and that it can play important role in oxidative phos phorylation. However, human AIF is also able to induce apoptosis. None of these effects could be inhibited by the pan caspase inhibitor z VAD fmk, thus they are caspase independent. Translocation of AIF into the nucleus occurs during apoptosis. The C.