Structural highlights
Function
[AREL1_HUMAN] E3 ubiquitin-protein ligase which accepts ubiquitin from an E2 ubiquitin-conjugating enzyme in the form of a thioester and then directly transfers the ubiquitin to targeted substrates. Inhibits apoptosis by ubiquitinating and targeting for degradation a number of proapoptotic proteins including DIABLO/SMAC, HTRA2 and SEPT4/ARTS which are released from the mitochondrion into the cytosol following apoptotic stimulation.[1]
Publication Abstract from PubMed
The HECT E3 ligase family comprises three subfamilies: NEDD4 E3 ubiquitin protein ligase (NEDD4), HECT and RLD domain-containing E3 ubiquitin protein ligase (HERC), and "other." Most previous studies have focused on the NEDD4 subfamily. Apoptosis-resistant E3 ligase 1 (AREL1) belongs to "other" subfamily HECT that inhibits apoptosis by ubiquitinating and degrading proapoptotic proteins. Here, we report the crystal structure of the extended HECT domain of AREL1 (436-823 aa) at 2.4 A resolution and its ubiquitination of the proapoptotic protein second mitochondria-derived activator of caspase (SMAC). We found that the extended HECT domain adopts an inverted, T-shaped, bilobed conformation and harbors an additional loop (567-573 aa) absent in all other HECT members. We also show that the N-terminal extended region (436-482 aa) preceding the HECT domain is indispensable for its stability and activity and that without this region, the HECT domain becomes inactive. AREL1 ubiquitinated SMAC, primarily on Lys-62 and Lys-191. We solved the crystal structure of tetrameric form of SMAC to 2.8 A resolution, revealing the Lys-62 and Lys-191 locations. The AREL1 HECT domain assembled Lys-33-, Lys-48- and Lys-63-linked polyubiquitin chains. Moreover, E701A substitution in the AREL1 HECT domain substantially increased its autopolyubiquitination and SMAC ubiquitination activity, whereas deletion of the last three amino acids at the C terminus completely abrogated AREL1 autoubiquitination and reduced SMAC ubiquitination. Finally, an AREL1-specific ubiquitin variant inhibited SMAC ubiquitination in vitro. Our findings may assist in the development of AREL1 inhibitors that block its anti-apoptotic activity in cancer.
Structural insights into a HECT-type E3 ligase AREL1 and its ubiquitination activities in vitro.,Singh S, Ng J, Nayak D, Sivaraman J J Biol Chem. 2019 Nov 15. pii: RA119.010327. doi: 10.1074/jbc.RA119.010327. PMID:31732561[2]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Kim JB, Kim SY, Kim BM, Lee H, Kim I, Yun J, Jo Y, Oh T, Jo Y, Chae HD, Shin DY. Identification of a novel anti-apoptotic E3 ubiquitin ligase that ubiquitinates antagonists of inhibitor of apoptosis proteins SMAC, HtrA2, and ARTS. J Biol Chem. 2013 Apr 26;288(17):12014-21. doi: 10.1074/jbc.M112.436113. Epub, 2013 Mar 11. PMID:23479728 doi:http://dx.doi.org/10.1074/jbc.M112.436113
- ↑ Singh S, Ng J, Nayak D, Sivaraman J. Structural insights into a HECT-type E3 ligase AREL1 and its ubiquitination activities in vitro. J Biol Chem. 2019 Nov 15. pii: RA119.010327. doi: 10.1074/jbc.RA119.010327. PMID:31732561 doi:http://dx.doi.org/10.1074/jbc.RA119.010327
