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HRD1-mediated ERAD tuning of ER-bound E2 is conserved between plants and mammals


When membrane proteins and secretory proteins are misfolded or incompletely folded, they are retained in the endoplasmic reticulum (ER) for further folding or degradation. The HMG-COA reductase degradation 1 (HRD1) and degradation of alpha2 10 (DOA10) complexes are two major components involved in the ER-associated protein degradation (ERAD) system in eukaryotic organisms14. However, the relationship between these two complexes is largely unknown, especially in higher eukaryotes. Here, we report that the plant ubiquitin-conjugating enzyme 32 (UBC32), an ER-bound E2 working in the DOA10 complex, is maintained at low levels under standard conditions by proteasome-dependent degradation mediated by the HRD1 complex, the other E3 complex involved in ERAD. Loss of this negative regulation under ER stress increases capacity for degradation of misfolded proteins retained in the ER. Consistently, UBE2J1, the homologue of UBC32 in mammals, was also identified to be targeted by HRD1 for degradation. Taken together, these results suggest that the regulation of UBC32 (or UBE2J1) by the HRD1 complex is conserved between plants and mammals.

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Figure 1: UBC32 is stabilized by knockout of key components of the HRD1 complex.
Figure 2: HRD1A and HRD1B interact with UBC32 and modulate the ubiquitylation and stability of UBC32.
Figure 3: UBC32 acts genetically downstream of the HRD1 complex and UBC32 is a versatile protein in facing different levels of stress.
Figure 4: UBE2J1 is targeted by HRD1 for proteasome system degradation.


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This research was supported by grant 973 Program 2011CB915402 from the National Basic Research Program of China and grant NSFC 31030047 from the National Science Foundation of China.

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Authors and Affiliations



Q.X. and Q.C. designed the research. Q.C., Y.W.Z., L.J.L., P.F.W., F.C. and Q.L.L. performed the research. Q.X., Q.C., Y.W.Z. and S.Y.F. analysed the data. Q.X. and Q.C. wrote the paper. S.Y.F., Y.R.W. and X.Y.Y. revised the manuscript.

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Correspondence to Qi Xie.

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The authors declare no competing financial interests.

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Supplementary Methods, Supplementary Figs 1-8, Supplementary Table 1 (PDF 950 kb)

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Chen, Q., Zhong, Y., Wu, Y. et al. HRD1-mediated ERAD tuning of ER-bound E2 is conserved between plants and mammals. Nature Plants 2, 16094 (2016).

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