title: SAG/RBX2 E3 ligase complexes with UBCH10 and UBE2S E2s to ubiquitylate β-TrCP1 via K11-linkage for degradation.
abstract: SAG/RBX2 and RBX1 are two family members of RING components of Cullin-RING ligases (CRLs), required for their enzymatic activity. Previous studies showed that SAG prefers to bind with CUL5, as well as CUL1, whereas RBX1 binds exclusively to CULs1-4. Detailed biochemical difference between SAG and RBX1, and whether SAG mediates cross-talk between CRL5 and CRL1 are previously unknown. Here we report that the levels of SAG and β-TrCP1 are inversely correlated, and SAG-CUL5-βTrCP1 forms a complex under physiological condition. SAG-CUL5, but not RBX1-CUL1, negatively modulates β-TrCP1 levels by shortening its protein half-life through promoting its ubiquitylation via atypical K11-linkage. Consistently, chemical inducers of SAG reduced β-TrCP1 level. Furthermore, SAG mainly binds to E2s UBCH10 and UBE2S known to mediate K11 linkage of ubiquitin, whereas RBX1 exclusively binds to E2s CDC34 and UBCH5C, known to mediate K48 linkage of ubiquitin. Finally, silencing of either UBCH10 or UBE2S, but not UBCH5C, caused accumulation of endogenous β-TrCP1, suggesting that β-TrCP1 is a physiological substrate of SAG-UBCH10C/UBE2S. Our study, for the first time, differentiates SAG and RBX1 biochemically via their respective binding to different E2s; and shows a negative cross-talk between CRL5 and CRL1 through SAG mediated ubiquitylation of β-TrCP1.
authors.affiliation: Department of Internal Medicine, Beijing University School of Medicine, 38 Xueyuan Road, Beijing, 100191, China.|Division of Radiation and Cancer Biology, Department of Radiation Oncology, University of Michigan, 4424B MS-1, 1301 Catherine Street, Ann Arbor, MI 48109, USA.
authors.forename: Peng
authors.initials: P
authors.lastname: Kuang
authors.affiliation: Division of Radiation and Cancer Biology, Department of Radiation Oncology, University of Michigan, 4424B MS-1, 1301 Catherine Street, Ann Arbor, MI 48109, USA.
authors.forename: Mingjia
authors.initials: M
authors.lastname: Tan
authors.affiliation: Division of Radiation and Cancer Biology, Department of Radiation Oncology, University of Michigan, 4424B MS-1, 1301 Catherine Street, Ann Arbor, MI 48109, USA.
authors.forename: Weihua
authors.initials: W
authors.lastname: Zhou
authors.affiliation: Division of Radiation and Cancer Biology, Department of Radiation Oncology, University of Michigan, 4424B MS-1, 1301 Catherine Street, Ann Arbor, MI 48109, USA.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Zhang
authors.affiliation: Division of Radiation and Cancer Biology, Department of Radiation Oncology, University of Michigan, 4424B MS-1, 1301 Catherine Street, Ann Arbor, MI 48109, USA.|Institute of Translational Medicine, Zhejiang University School of Medicine, Hangzhou, Zhejiang, People's Republic of China.|Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Zhejiang University, Hangzhou, P. R. China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Sun
mesh_terms: D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D044842:Cullin Proteins / Q000235:genetics / Q000378:metabolism; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism*; D005786:Gene Expression Regulation; D057809:HEK293 Cells; D006207:Half-Life; D006801:Humans; D008239:Lysine / Q000378:metabolism*; D051379:Mice; D000066450:Mouse Embryonic Stem Cells / Q000166:cytology / Q000378:metabolism; D011485:Protein Binding; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D059748:Proteolysis; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D044763:Ubiquitin-Conjugating Enzymes / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000235:genetics* / Q000378:metabolism; D054875:Ubiquitination; D044844:beta-Transducin Repeat-Containing Proteins / Q000235:genetics* / Q000378:metabolism
chemical_list: C471644:BTRC protein, human; D002352:Carrier Proteins; C100318:Cullin 1; D044842:Cullin Proteins; D020033:Protein Isoforms; C479529:RBX1 protein, human; D034741:RNA, Small Interfering; D044844:beta-Transducin Repeat-Containing Proteins; C577447:CDC34 protein, human; C105156:UBE2C protein, human; C097310:UBE2D3 protein, human; C544962:Ube2S protein, human; D044763:Ubiquitin-Conjugating Enzymes; C118307:RNF7 protein, human; D044767:Ubiquitin-Protein Ligases; D008239:Lysine