The zinc finger protein A20 interacts with a novel anti-apoptotic protein which is cleaved by specific caspases.
A20 is a Cys2/Cys2 zinc finger protein which is induced by a variety of inflammatory stimuli and which has been characterized as an inhibitor of cell death by a yet unknown mechanism. In order to clarify its molecular mechanism of action, we used the yeast two-hybrid system to screen for proteins that interact with A20. A cDNA fragment was isolated which encoded a portion of a novel protein (TXBP151), which was recently found to be a human T-cell leukemia virus type-I (HTLV-I) Tax-binding protein. The full-length 2386 bp TXBP151 mRNA encodes a protein of 86 kDa. Like A20, overexpression of TXBP151 could inhibit apoptosis induced by tumour necrosis factor (TNF) in NIH3T3 cells. Moreover, transfection of antisense TXBP151 partially abolished the anti-apoptotic effect of A20. Furthermore, apoptosis induced by TNF or CD95 (Fas/APO-1) was associated with proteolysis of TXBP151. This degradation could be inhibited by the broad-spectrum caspase inhibitor zVAD-fmk or by expression of the cowpox virus-derived inhibitor CrmA, suggesting that TXBP151 is a novel substrate for caspase family members. TXBP151 was indeed found to be specifically cleaved in vitro by members of the caspase-3-like subfamily, viz. caspase-3, caspase-6 and caspase-7. Thus TXBP151 appears to be a novel A20-binding protein which might mediate the anti-apoptotic activity of A20, and which can be processed by specific caspases.
Pubmed ID: 10435631 RIS Download
3T3 Cells | Amino Acid Chloromethyl Ketones | Amino Acid Sequence | Animals | Antigens, CD95 | Apoptosis | Base Sequence | Carrier Proteins | Caspases | Cell Line | Cloning, Molecular | Cysteine Endopeptidases | Cysteine Proteinase Inhibitors | DNA, Complementary | DNA-Binding Proteins | Dactinomycin | Genes | HeLa Cells | Humans | Intracellular Signaling Peptides and Proteins | Mice | Molecular Sequence Data | Neoplasm Proteins | Nuclear Proteins | Nucleic Acid Synthesis Inhibitors | Oligonucleotides, Antisense | Protein Binding | Protein Processing, Post-Translational | Proteins | RNA, Messenger | Recombinant Fusion Proteins | Saccharomyces cerevisiae | Serpins | Substrate Specificity | Transfection | Tumor Necrosis Factor-alpha | Viral Proteins | Zinc Fingers