Structural insights into a HECT-type E3 ligase AREL1 and its ubiquitination activities in vitro
- National Univ. of Singapore (Singapore)
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. In this paper, we report the crystal structure of the extended HECT domain of AREL1 (amino acids (aa) 436–823) at 2.4 Å 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 (aa 567–573) absent in all other HECT members. We also show that the N-terminal extended region (aa 436–482) 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 Lys62 and Lys191. We solved the crystal structure of the tetrameric form of SMAC to 2.8 Å resolution, revealing the Lys62 and Lys191 locations. The AREL1 HECT domain assembled Lys33-, Lys48-, and Lys63-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 biquitination. 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.
- Research Organization:
- Argonne National Laboratory (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
- Sponsoring Organization:
- National Institute of General Medical Sciences (NIGMS); National Institutes of Health (NIH); Ministry of Education, Singapore; USDOE
- Grant/Contract Number:
- P41 GM103403; S10 RR029205; AC02-06CH11357; R-154-000-B03-112 (MoE Tier 2); R154-000-A72-114 (AcRF Tier 1)
- OSTI ID:
- 1591895
- Journal Information:
- Journal of Biological Chemistry, Vol. 294, Issue 52; ISSN 0021-9258
- Publisher:
- American Society for Biochemistry and Molecular BiologyCopyright Statement
- Country of Publication:
- United States
- Language:
- ENGLISH
Web of Science
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Related Subjects
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
apoptosis
E3 ubiquitin ligase
ubiquitylation (ubiquitination)
crystal structure
structure-function
structural biology
protein degradation
post-translational modification (PTM)
cancer apoptosis-resistant E3 ligase 1 (AREL1)
autopolyubiquitination
HECT domain
second mitochondria-derived activator of caspase (SMAC)