Coxsackievirus B5 induced apoptosis of HeLa cells: Effects on p53 and SUMO

Accumulating evidence suggests that viruses hijack cellular proteins to circumvent the host immune system. Ubiquitination and SUMOylation are extensively studied posttranslational modifications (PTMs) that play critical roles in diverse biological processes. Cross talk between ubiquitination and SUMOylation of both host and viral proteins has been reported to result in distinct functional consequences. Enterovirus 71 (EV71), an RNA virus belonging to the family Picornaviridae, is a common cause of hand, foot, and mouth disease. Little is known concerning how host PTM systems interact with enteroviruses. Here, we demonstrate that the 3D protein, an RNA-dependent RNA polymerase (RdRp) of EV71, is modified by small ubiquitin-like modifier 1 (SUMO-1) both during infection and in vitro. Residues K159 and L150/D151/L152 were responsible for 3D SUMOylation as determined by bioinformatics prediction combined with site-directed mutagenesis. Also, primer-dependent polymerase assays indicated that mutation of SUMOylation sites impaired 3D polymerase activity and virus replication. Moreover, 3D is ubiquitinated in a SUMO-dependent manner, and SUMOylation is crucial for 3D stability, which may be due to the interplay between the two PTMs. Importantly, increasing the level of SUMO-1 in EV71-infected cells augmented the SUMOylation and ubiquitination levels of 3D, leading to enhanced replication of EV71. These results together suggested that SUMO and ubiquitin cooperatively regulated EV71 infection, either by SUMO-ubiquitin hybrid chains or by ubiquitin conjugating to the exposed lysine residue through SUMOylation. Our study provides new insight into how a virus utilizes cellular pathways to facilitate its replication. IMPORTANCEInfection with enterovirus 71 (EV71) often causes neurological diseases in children, and EV71 is responsible for the majority of fatalities. Based on a better understanding of interplay between virus and host cell, antiviral drugs against enteroviruses may be developed. As a dynamic cellular process of posttranslational modification, SUMOylation regulates global cellular protein localization, interaction, stability, and enzymatic activity. However, little is known concerning how SUMOylation directly influences virus replication by targeting viral polymerase. Here, we found that EV71 polymerase 3D was SUMOylated during EV71 infection and in vitro. Moreover, the SUMOylation sites were determined, and in vitro polymerase assays indicated that mutations at SUMOylation sites could impair polymerase synthesis. Importantly, 3D is ubiquitinated in a SUMOylation-dependent manner that enhances the stability of the viral polymerase. Our findings indicate that the two modifications likely cooperatively enhance virus replication. Our study may offer a new therapeutic strategy against virus replication. S mall ubiquitin-like modifier (SUMO) modification, a member of the group of posttranslational modifications (PTMs), is important for the regulation of many cellular proteins and pathways (1). SUMO is a novel...

Section: Discussionmentioning

confidence: 99%

SUMO Modification Stabilizes Enterovirus 71 Polymerase 3D To Facilitate Viral Replication

Liu

Zheng

Shu

et al. 2016

“…At least three classes of SUMO E3-ligases have been reported, RanBP2, PIAS, and the polycomb protein Pc2. A recent report shows that CVB5 infection results in cytoplasmic redistribution of SUMO-1 and UBC9 (8).…”

Section: Effect Of Reg␥ Knockdown or Overexpression On Coxsackieviralmentioning

confidence: 95%

Proteasome Activator REGγ Enhances Coxsackieviral Infection by Facilitating p53 Degradation

Gao

Wong

Zhang

et al. 2010

Coxsackievirus B3 (CVB3) is a small RNA virus associated with diseases such as myocarditis, meningitis, and pancreatitis. We have previously demonstrated that proteasome inhibition reduces CVB3 replication and attenuates virus-induced myocarditis. However, the underlying mechanisms by which the ubiquitin/proteasome system regulates CVB replication remain unclear. In this study, we investigated the role of REG␥, a member of the 11S proteasome activator, in CVB3 replication. We showed that overexpression of REG␥ promoted CVB3 replication but that knockdown of REG␥ led to reduced CVB3 replication. We further demonstrated that REG␥-mediated p53 proteolysis contributes, as least in part, to the proviral function of REG␥. Although total protein levels of REG␥ remained unaltered after CVB3 infection, virus infection induced a redistribution of REG␥ from the nucleus to the cytoplasm, rendering an opportunity for a direct interaction of REG␥ with viral proteins and/or host proteins (e.g., p53), which controls viral growth and thereby enhances viral infectivity. Further analyses suggested a potential modification of REG␥ by SUMO following CVB3 infection, which was verified by both in vitro and in vivo sumoylation assays. Sumoylation of REG␥ may play a role in its nuclear export during CVB3 infection. Taken together, our results present the first evidence that the host REG␥ pathway is utilized and modified during CVB3 infection to promote efficient viral replication.Viruses often adapt to the existing host cellular machinery to complete their own life cycle. The ubiquitin/proteasome system (UPS), a primary intracellular protein degradation system in eukaryotic cells, has emerged as a key modulator in viral infectivity and virus-mediated pathogenesis (6).Coxsackievirus B3 (CVB3) is a small RNA virus associated with diseases such as myocarditis, meningitis, and pancreatitis (36). We have previously studied the function and regulation of the UPS in CVB3 infection and CVB3-induced myocarditis (7,16,17,33). We demonstrated that CVB3 utilizes and manipulates the host UPS to achieve successful replication (17, 33). We provided evidence that proteasome inhibition reduces CVB3 replication and attenuates virus-induced myocarditis (7). However, we recognize the potential toxicity of general inhibition of proteasome function as a therapeutic means. Further investigation to identify specific targets within the UPS utilized during CVB3 infection is urgently needed and will allow for more-precise targeting in drug therapy.The 20S proteasome is a multisubunit protease complex responsible for the degradation of misfolded proteins or shortlived regulatory proteins (16,18). In the absence of proteasome activators, the 20S proteasome is latent and the protein substrates are barred from entering the 20S proteasome (16,18). There are at least two families of proteasome activators, the 19S proteasome (also known as PA700) and the 11S proteasome (also known as REG or PA28) (16, 18). The 19S activator binds to proteasome to form the 26S proteasome...

“…Evidence from clinically isolated strains support the hypothesis that SUMO modification and the Ubc9/3C interaction have important medical implications, while posttranslational modification of 3C serves as a host cell defense mechanism counteracted by evolving sitespecific EV71 escape mutants (30). Although coxsackievirus B5 influences the host cell SUMOylation system to some extent (61), far more research is necessary to define the role of this PTM for picornaviruses in general.…”

Section: Rna Virusesmentioning

confidence: 99%

Human Pathogens and the Host Cell SUMOylation System

Wimmer

Schreiner

Dobner

2012

111

101

Since posttranslational modification (PTM) by the small ubiquitin-related modifiers (SUMOs) was discovered over a decade ago, a huge number of cellular proteins have been found to be reversibly modified, resulting in alteration of differential cellular pathways. Although the molecular consequences of SUMO attachment are difficult to predict, the underlying principle of SUMOylation is altering inter-and/or intramolecular interactions of the modified substrate, changing localization, stability, and/or activity. Unsurprisingly, many different pathogens have evolved to exploit the cellular SUMO modification system due to its functional flexibility and far-reaching functional downstream consequences. Although the extensive knowledge gained so far is impressive, a definitive conclusion about the role of SUMO modification during virus infection in general remains elusive and is still restricted to a few, yet promising concepts. Based on the available data, this review aims, first, to provide a detailed overview of the current state of knowledge and, second, to evaluate the currently known common principles/molecular mechanisms of how human pathogenic microbes, especially viruses and their regulatory proteins, exploit the host cell SUMO modification system. Small ubiquitin-related modifier (SUMO) was initially identified as reversible, proteinogenic posttranslational modification (PTM) by different laboratories in the mid-1990s (13,116,122,125,135). Today, it is classified as a member of the ubiquitin-like proteins (Ubls) due to its structural and sequence similarities to ubiquitin (89, 169); however, the surface properties of SUMO are quite distinct. Interestingly, it appears that the characteristic determinants of PTM by Ubls are phylogenetically ancient and may have evolved from biosynthetic pathways via repeated rounds of gene duplication and diversification (75). Consequently, SUMO is expressed by all eukaryotes but is absent from prokaryotes/archaea. Lower eukaryotes have a single SUMO gene, whereas plants and vertebrates express several SUMO paralogues.In vertebrates, two subfamilies, namely, SUMO-1 and SUMO-2/3 proteins, are known. SUMO-2 and SUMO-3 are commonly referred to as SUMO-2/3 due to 98% sequence similarity and the lack, to date, of clearly distinguishable functional differences. Although members of each subfamily are highly similar, SUMO-1 and SUMO-2/3 share only about 50% amino acid sequence identity, although all are ϳ100-residue proteins containing significant primary sequence homology to ubiquitin in the C terminus (ϳ20%) and a short unstructured N-terminal stretch (11,128).Recent research has shown important differences in the molecular functionalities of mammalian SUMO-1 and SUMO-2/3 proteins. The latter is present in higher levels than SUMO-1, whereas the unconjugated pool of SUMO-1 is lower than that of SUMO-2/3. Intriguingly, SUMO-2 and SUMO-3 can be conjugated to target proteins in a chain-wise fashion due to internal SUMO conjugation motifs (SCMs), whereas SUMO-1 lacks this ability. Moreover...