Identification of inhibitor of apoptosis specific DNase in Xenopus egg extract

When added with cytochrome c, Xenopus laevis egg extract XS-150 can induce exogenous nuclei undergoing apoptosis. Apoptosis specific DNase XAD was act ivated during this process, and cut chromatin between nucleosome, leading t o DNA Ladder in electrophoresis. Our results showed that an inhibitor of XA D, IXAD, exists abundantly in normal egg extract, its molecular weight is a bout 40 ku. Normally, IXAD exists either in the form of dimmer or in comple x with NAD. It was degraded during apoptosis, releasing active XAD. The res ults of Western assay and cross-inhibition showed that MAD was likely homol ogous to DFF45 in structure and function. At the same time, these results a lso indicated that the pathway in apoptosis was conserved in evolution.