TAILIEUCHUNG - Báo cáo khoa học: Apoptosis-inhibiting activities of BIR family proteins in Xenopus egg extracts

In many animal species includingXenopus, ovulated eggs possess an intrin-sic apoptotic execution system. This program is inhibited for a limited time by some maternal apoptosis inhibitors, although their molecular properties remain uncharacterized. Baculovirus IAP repeat (BIR) family proteins con-tain evolutionarily conserved BIR domains and play important roles in apoptosis suppression, and are therefore good candidates as maternal apoptosis inhibitors. | ềFEBS Journal Apoptosis-inhibiting activities of BIR family proteins in Xenopus egg extracts Yuichi Tsuchiya Shin Murai and Shigeru Yamashita Department of Biochemistry Toho University Schoolof Medicine Tokyo Japan Keywords apoptosis inhibitor survivin Xenopus egg extracts XIAP XLX Correspondence S. Yamashita Department of Biochemistry Toho University Schoolof Medicine 5-21-16 Omori-nishi Ota-ku 143-8540 Tokyo Japan Fax 81 3 5493 5412 Tel 81 3 3762 4151 ext. 2356 E-mail yamasita@ Note Nucleotide sequence data are available in the DDBJ EMBL GenBank databases under the accession numbers AB197247 AB197249 AB197251 and AB197252. Received 11 January 2005 revised 1 March 2005 accepted 7 March 2005 doi In many animal species including Xenopus ovulated eggs possess an intrinsic apoptotic execution system. This program is inhibited for a limited time by some maternal apoptosis inhibitors although their molecular properties remain uncharacterized. Baculovirus IAP repeat BIR family proteins contain evolutionarily conserved BIR domains and play important roles in apoptosis suppression and are therefore good candidates as maternal apoptosis inhibitors. We identified four maternal BIR family proteins in Xenopus eggs and using the biochemical advantages of egg extracts examined their physiological functions. These molecules included two survivin-related proteins xEIAP XLX and a possible ortholog of XIAP named xXIAP. The addition of recombinant xXIAP greatly delayed apoptotic execution whereas the immunodepletion of endogenous xXIAP significantly accelerated the onset of apoptosis. In contrast xEIAP XLX was a poor apoptosis inhibitor and neither of the survivin orthologs showed anti-apoptotic activity in our assay. Both xEIAP XLX and xXIAP were degraded by activated caspases and also by a novel proteolytic system that required the presence of C-terminal RING finger domain but was insensitive to proteasome inhibition. Our data .

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