Ubiquitin-Like protein 5 interacts with the silencing suppressor p3 of rice stripe virus and mediates its degradation through the 26S proteasome pathway.

Binghua Chen,Junmin Li,Lin Lin,Baoan Song,Shaofei Rao,Zhuo Chen,Guanwei Wu,Jianping Chen,Fei Yan,Hongying Zheng,Jiejun Peng,Yuwen Lu,Qiankun Yang,Hui-Shan Guo

doi:10.1371/journal.ppat.1008780

Binghua Chen, Junmin Li + Show 12 more

Open Access

https://doi.org/10.1371/journal.ppat.1008780

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Abstract

Ubiquitin like protein 5 (UBL5) interacts with other proteins to regulate their function but differs from ubiquitin and other UBLs because it does not form covalent conjugates. Ubiquitin and most UBLs mediate the degradation of target proteins through the 26S proteasome but it is not known if UBL5 can also do that. Here we found that the UBL5s of rice and Nicotiana benthamiana interacted with rice stripe virus (RSV) p3 protein. Silencing of NbUBL5s in N. benthamiana facilitated RSV infection, while UBL5 overexpression conferred resistance to RSV in both N. benthamiana and rice. Further analysis showed that NbUBL5.1 impaired the function of p3 as a suppressor of silencing by degrading it through the 26S proteasome. NbUBL5.1 and OsUBL5 interacted with RPN10 and RPN13, the receptors of ubiquitin in the 26S proteasome. Furthermore, silencing of NbRPN10 or NbRPN13 compromised the degradation of p3 mediated by NbUBL5.1. Together, the results suggest that UBL5 mediates the degradation of RSV p3 protein through the 26S proteasome, a previously unreported plant defense strategy against RSV infection.

Highlights

Ubiquitin is a 76-residue (8.6 kDa) regulatory protein that is conserved throughout the eukaryotic kingdom [1, 2]
We here found that the 26S proteasome degraded the p3 suppressor of RNA silencing of rice stripe virus to inhibit viral infection, and that the degradation was mediated by ubiquitin-like protein 5 (UBL5) but not by ubiquitin
Ubiquitinlike protein 5 (UBL5) interacts with rice stripe virus (RSV) p3 protein and mediates its degradation through the 26S proteasome pathway

Summary

Introduction

Ubiquitin is a 76-residue (8.6 kDa) regulatory protein that is conserved throughout the eukaryotic kingdom [1, 2]. UBLs range in size from 73 to 186 amino acids and share a canonical three-dimensional structure called the ubiquitin-fold [3, 7,8,9,10,11]. Many UBLs, such as SUMO (small ubiquitin-related modifier), NEDD8 (neural precursor cell expressed, developmentally down-regulated 8) and ISG15 (interferon-stimulated gene 15), bind to target proteins for regulation though the sequential activities of an E1-E3 enzymatic cascade [12,13,14]. UBL5/Hub is evolutionarily conserved and shares a low degree of sequence similarity with ubiquitin, yet closely resembles it structurally [15, 17,18,19]

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