title: TRIM39 is a MOAP-1-binding protein that stabilizes MOAP-1 through inhibition of its poly-ubiquitination process.
abstract: Bax, a multi-domain pro-apoptotic Bcl-2 family member, is a key regulator for the release of apoptogenic factors from mitochondria. MOAP-1, which was first isolated from a screen for Bax-associating proteins, interacts with Bax upon apoptotic induction. MOAP-1 is a short-lived protein that is constitutively degraded by the ubiquitin-proteasome system. Apoptotic stimuli upregulate MOAP-1 rapidly through inhibition of its poly-ubiquitination process. However, cellular factors that regulate the stability of MOAP-1 have not yet been identified. In this study, we report the identification of TRIM39 as a MOAP-1-binding protein. TRIM39 belongs to a family of proteins characterized by a Tripartite Motif (TRIM), consisting of RING domain, B-box and coiled-coil domain. Several TRIM family members are known to demonstrate E3 ubiquitin ligase activity. Surprisingly, TRIM39 significantly extends the half-life of MOAP-1 by inhibiting its poly-ubiquitination process. In agreement with its effect on enhancing MOAP-1 stability, TRIM39 sensitizes cells to etoposide-induced apoptosis. Conversely, knockdown of TRIM39 reduces the sensitivity of cells to etoposide-stimulated apoptosis. Furthermore, TRIM39 elevates the level of MOAP-1 in mitochondria and promotes cytochrome c release from isolated mitochondria stimulated by recombinant Bax. Together, these data suggest that TRIM39 can promote apoptosis signalling through stabilization of MOAP-1.
authors.affiliation: Institute of Molecular and Cell Biology, A*STAR (Agency for Science, Technology and Research), Singapore 138673, Singapore.
authors.forename: San San
authors.initials: SS
authors.lastname: Lee
authors.forename: Nai Yang
authors.initials: NY
authors.lastname: Fu
authors.forename: Sunil K
authors.initials: SK
authors.lastname: Sukumaran
authors.forename: Kah Fei
authors.initials: KF
authors.lastname: Wan
authors.forename: Qian
authors.initials: Q
authors.lastname: Wan
authors.forename: Victor C
authors.initials: VC
authors.lastname: Yu
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis / Q000502:physiology; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D045304:Cytochromes c / Q000378:metabolism; D006801:Humans; D008928:Mitochondria / Q000378:metabolism; D008969:Molecular Sequence Data; D025821:Polyubiquitin / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D020798:Two-Hybrid System Techniques; D044767:Ubiquitin-Protein Ligases; D054875:Ubiquitination; D051028:bcl-2-Associated X Protein / Q000235:genetics / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D051017:Apoptosis Regulatory Proteins; D002352:Carrier Proteins; C428449:MOAP1 protein, human; D051028:bcl-2-Associated X Protein; D025821:Polyubiquitin; D045304:Cytochromes c; C414583:TRIM39 protein, human; D044767:Ubiquitin-Protein Ligases