Identification of a Bcl-XL binding region within the ATPase domain of Apaf-1 |
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Authors: | Yajima Hirohiko Suzuki Fumio |
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Institution: | Department of Molecular Radiobiology, Research Institute for Radiation Biology and Medicine, Hiroshima University, Hiroshima 734-8553, Japan. yajima@hiroshima-u.ac.jp |
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Abstract: | CED-4, a pro-apoptotic factor in Caenorhabditis elegans, activates the cell death protease CED-3. CED-9 directly binds to CED-4 and represses this. However, it has remained unclear whether a mammalian CED-9 homologue, Bcl-XL, inhibits the function of the mammalian CED-4 homologue, Apaf-1, by direct binding. To analyze the interaction, we adopted a yeast two-hybrid system. Since Bcl-XL and the CED-4-like portion of Apaf-1 failed to exhibit a positive result in the assay, we prepared "fragment libraries" of bcl-XL or apaf-1 cDNA. By screening of the apaf-1 "fragment library," we obtained nine clones interacting with Bcl-XL, all containing the same region within the ATPase domain, designated BBR: the Bcl-XL binding region. Binding of BBR to Bcl-XL was also confirmed by immunoprecipitation assays. Bcl-2, Bcl-w, A1/Bfl-1, and Boo/Diva failed to show the same capacity for binding to BBR as Bcl-XL. These results indicate that Bcl-XL directly binds to a specific region in Apaf-1. |
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Keywords: | Apoptosis Apaf-1 Bcl-XL CED-4 CED-9 Two-hybrid system Immunoprecipitation Direct binding |
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