Snapshots of ADP-ribose bound to Getah virus macro domain reveal an intriguing choreography.
ABSTRACT: Alphaviruses are (re-)emerging arboviruses of public health concern. The nsP3 gene product is one of the key players during viral replication. NsP3 comprises three domains: a macro domain, a zinc-binding domain and a hypervariable region. The macro domain is essential at both early and late stages of the replication cycle through ADP-ribose (ADPr) binding and de-ADP-ribosylation of host proteins. However, both its specific role and the precise molecular mechanism of de-ADP-ribosylation across specific viral families remains to be elucidated. Here we investigate by X-ray crystallography the mechanism of ADPr reactivity in the active site of Getah virus macro domain, which displays a peculiar substitution of one of the conserved residues in the catalytic loop. ADPr adopts distinct poses including a covalent bond between the C''1 of the ADPr and a conserved Togaviridae-specific cysteine. These different poses observed for ADPr may represent snapshots of the de-ADP-ribosylation mechanism, highlighting residues to be further characterised.
Project description:Venezuelan equine encephalitis virus (VEEV) is a new world alphavirus which can be involved in several central nervous system disorders such as encephalitis and meningitis. The VEEV genome codes for 4 non-structural proteins (nsP), of which nsP3 contains a Macro domain. Macro domains (MD) can be found as stand-alone proteins or embedded within larger proteins in viruses, bacteria and eukaryotes. Their most common feature is the binding of ADP-ribose (ADPr), while several macro domains act as ribosylation writers, erasers or readers. Alphavirus MD erase ribosylation but their precise contribution in viral replication is still under investigation. NMR-driven titration experiments of ADPr in solution with the VEEV macro domain (in apo- and complex state) show that it adopts a suitable conformation for ADPr binding. Specific experiments indicate that the flexibility of the loops ?5-?3 and ?3-?6 is critical for formation of the complex and assists a wrapping mechanism for ADPr binding. Furthermore, along with this sequence of events, the VEEV MD undergoes a conformational exchange process between the apo state and a low-populated "dark" conformational state.
Project description:The pandemic outbreak of a novel coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has threatened the global public health and economy since late December 2019. SARS-CoV-2 encodes the conserved macro domain within nonstructural protein 3, which may reverse cellular ADP-ribosylation and potentially cut the signal of a viral infection in the cell. Herein, we report that the SARS-CoV-2 macro domain was examined as a poly-ADP-ribose (ADPR) binding module and possessed mono-ADPR cleavage enzyme activity. After confirming the ADPR binding ability via a biophysical approach, the X-ray crystal structure of the SARS-CoV-2 macro domain was determined and structurally compared with those of other viruses. This study provides structural, biophysical, and biochemical bases to further evaluate the role of the SARS-CoV-2 macro domain in the host response via ADP-ribose binding but also as a potential target for drug design against COVID-19.
Project description:Protein ADP-ribosylation is a reversible post-translational modification that regulates important cellular functions. The identification of modified proteins has proven challenging and has mainly been achieved via enrichment methodologies. Random mutagenesis was used here to develop an engineered Af1521 ADP-ribose binding macro domain protein with 1000-fold increased affinity towards ADP-ribose. The crystal structure reveals that two point mutations K35E and Y145R form a salt bridge within the ADP-ribose binding domain. This forces the proximal ribose to rotate within the binding pocket and, as a consequence, improves engineered Af1521 ADPr-binding affinity. Its use in our proteomic ADP-ribosylome workflow increases the ADP-ribosylated protein identification rates and yields greater ADP-ribosylome coverage. Furthermore, generation of an engineered Af1521 Fc fusion protein confirms the improved detection of cellular ADP-ribosylation by immunoblot and immunofluorescence. Thus, this engineered isoform of Af1521 can also serve as a valuable tool for the analysis of cellular ADP-ribosylation under in vivo conditions.
Project description:UNLABELLED:ADP-ribosylation is a posttranslational protein modification in which ADP-ribose is transferred from NAD(+) to specific acceptors to regulate a wide variety of cellular processes. The macro domain is an ancient and highly evolutionarily conserved protein domain widely distributed throughout all kingdoms of life, including viruses. The human TARG1/C6orf130, MacroD1, and MacroD2 proteins can reverse ADP-ribosylation by acting on ADP-ribosylated substrates through the hydrolytic activity of their macro domains. Here, we report that the macro domain from hepatitis E virus (HEV) serves as an ADP-ribose-protein hydrolase for mono-ADP-ribose (MAR) and poly(ADP-ribose) (PAR) chain removal (de-MARylation and de-PARylation, respectively) from mono- and poly(ADP)-ribosylated proteins, respectively. The presence of the HEV helicase in cis dramatically increases the binding of the macro domain to poly(ADP-ribose) and stimulates the de-PARylation activity. Abrogation of the latter dramatically decreases replication of an HEV subgenomic replicon. The de-MARylation activity is present in all three pathogenic positive-sense, single-stranded RNA [(+)ssRNA] virus families which carry a macro domain: Coronaviridae (severe acute respiratory syndrome coronavirus and human coronavirus 229E), Togaviridae (Venezuelan equine encephalitis virus), and Hepeviridae (HEV), indicating that it might be a significant tropism and/or pathogenic determinant. IMPORTANCE:Protein ADP-ribosylation is a covalent posttranslational modification regulating cellular protein activities in a dynamic fashion to modulate and coordinate a variety of cellular processes. Three viral families, Coronaviridae, Togaviridae, and Hepeviridae, possess macro domains embedded in their polyproteins. Here, we show that viral macro domains reverse cellular ADP-ribosylation, potentially cutting the signal of a viral infection in the cell. Various poly(ADP-ribose) polymerases which are notorious guardians of cellular integrity are demodified by macro domains from members of these virus families. In the case of hepatitis E virus, the adjacent viral helicase domain dramatically increases the binding of the macro domain to PAR and simulates the demodification activity.
Project description:Chromatin ADP-ribosylation regulates important cellular processes. However, the exact location and magnitude of chromatin ADP-ribosylation are largely unknown. A robust and versatile method for assessing chromatin ADP-ribosylation is therefore crucial for further understanding its function. Here, we present a chromatin affinity precipitation method based on the high specificity and avidity of two well-characterized ADP-ribose binding domains to map chromatin ADP-ribosylation at the genome-wide scale and at specific loci. Our ADPr-ChAP method revealed that in cells exposed to oxidative stress, ADP-ribosylation of chromatin scaled with histone density, with highest levels at heterochromatic sites and depletion at active promoters. Furthermore, in growth factor-induced adipocyte differentiation, increased chromatin ADP-ribosylation was observed at PPARγ target genes, whose expression is ADP-ribosylation-dependent. In combination with deep-sequencing and conventional ChIP, the established ADPr-ChAP provides a valuable resource for the bioinformatic comparison of ADP-ribosylation with other chromatin modifications and for addressing its role in other biologically important processes. Overall design: Chromatin of untreated and H2O2-treated samples was pulled down with wild-type and R163A-mutant WWE domain. We performed ChAP followed by DNA-sequencinq of sheared chromatin from untreated cells enriched with wild-type RNF146 WWE domain to define the location of ADP-ribosylation in untreated cells, using the binding mutant as negative control. In addition, as oxidative stress is known to induce chromatin ADP-ribosilation, we include ChAP followed by DNA-sequencinq of sheared chromatin from H2O2-treated cells enriched with wild-type RNF146 WWE or the binding mutant.
Project description:Sindbis virus (SINV), the prototype alphavirus, contains a macro domain in the highly conserved N-terminal region of nonstructural protein 3 (nsP3). However, the biological role of the macro domain is unclear. Mutations of amino acids 10 and 24 from asparagine to alanine in the ADP-ribose binding region of the macro domain impaired SINV replication and viral RNA synthesis particularly in neurons, but did not alter binding of poly(ADP-ribose). Mutation at position 10 had the greatest effect and caused nsP3 instability in neurons, decreased SINV-induced death of mature, but not immature neurons, and attenuated virulence in 2 week-old, but not 5 day-old mice. A compensatory mutation at amino acid 31 in the macro domain of nsP3, as well as reversion of mutated amino acid 10, occurred during replication of double mutant SINV in vitro and in vivo. The nsP3 macro domain is important for SINV replication and age-dependent susceptibility to encephalomyelitis.
Project description:BACKGROUND: The identification of new virus strains is important for the study of infectious disease, but current (or existing) molecular biology methods are limited since the target sequence must be known to design genome-specific PCR primers. Thus, we developed a new method for the discovery of unknown viruses based on the cDNA--random amplified polymorphic DNA (cDNA-RAPD) technique. Getah virus, belonging to the family Togaviridae in the genus Alphavirus, is a mosquito-borne enveloped RNA virus that was identified using the Virus-Discovery-cDNA RAPD (VIDISCR) method. RESULTS: A novel Getah virus was identified by VIDISCR from suckling mice exposed to mosquitoes (Aedes albopictus) collected in Yunnan Province, China. The non-structural protein gene, nsP3, the structural protein gene, the capsid protein gene, and the 3'-untranslated region (UTR) of the novel Getah virus isolate were cloned and sequenced. Nucleotide sequence identities of each gene were determined to be 97.1-99.3%, 94.9-99.4%, and 93.6-99.9%, respectively, when compared with the genomes of 10 other representative strains of Getah virus. CONCLUSIONS: The VIDISCR method was able to identify known virus isolates and a novel isolate of Getah virus from infected mice. Phylogenetic analysis indicated that the YN08 isolate was more closely related to the Hebei HB0234 strain than the YN0540 strain, and more genetically distinct from the MM2021 Malaysia primitive strain.
Project description:ADP-ribosylation is a reversible post-translational modification with wide-ranging biological functions in all kingdoms of life. A variety of enzymes use NAD(+) to transfer either single or multiple ADP-ribose (ADPr) moieties onto distinct amino acid substrates, often in response to DNA damage or other stresses. Poly-ADPr-glycohydrolase readily reverses poly-ADP-ribosylation induced by the DNA-damage sensor PARP1 and other enzymes, but it does not remove the most proximal ADPr linked to the target amino acid. Searches for enzymes capable of fully reversing cellular mono-ADP-ribosylation back to the unmodified state have proved elusive, which leaves a gap in the understanding of this modification. Here, we identify a family of macrodomain enzymes present in viruses, yeast and animals that reverse cellular ADP-ribosylation by acting on mono-ADP-ribosylated substrates. Our discoveries establish the complete reversibility of PARP-catalyzed cellular ADP-ribosylation as a regulatory modification.
Project description:The macro domain is an ADP-ribose (ADPR) binding module, which is considered to act as a sensor to recognize nicotinamide adenine dinucleotide (NAD) metabolites, including poly ADPR (PAR) and other small molecules. The recognition of macro domains with various ligands is important for a variety of biological functions involved in NAD metabolism, including DNA repair, chromatin remodeling, maintenance of genomic stability, and response to viral infection. Nevertheless, how the macro domain binds to moieties with such structural obstacles using a simple cleft remains a puzzle. We systematically investigated the Middle East respiratory syndrome-coronavirus (MERS-CoV) macro domain for its ligand selectivity and binding properties by structural and biophysical approaches. Of interest, NAD, which is considered not to interact with macro domains, was co-crystallized with the MERS-CoV macro domain. Further studies at physiological temperature revealed that NAD has similar binding ability with ADPR because of the accommodation of the thermal-tunable binding pocket. This study provides the biochemical and structural bases of the detailed ligand-binding mode of the MERS-CoV macro domain. In addition, our observation of enhanced binding affinity of the MERS-CoV macro domain to NAD at physiological temperature highlights the need for further study to reveal the biological functions.
Project description:ADP-ribosylation is an enzyme-catalyzed post-translational modification of proteins in which the ADP-ribose (ADPR) moiety of NAD+ is transferred to a specific amino acid in a substrate protein. The biological functions of ADP-ribosylation are numerous and diverse, ranging from normal physiology to pathological conditions. Biochemical and cellular studies of the diverse forms and functions of ADPR require immunological reagents that can be used for detection and enrichment. The lack of a complete set of tools that recognize all forms of ADPR [i.e., mono-, oligo-, and poly(ADP-ribose)] has hampered progress. Herein, we describe the generation and characterization of a set of recombinant antibody-like ADP-ribose binding proteins, in which naturally occurring ADPR binding domains, including macrodomains and WWE domains, have been functionalized by fusion to the Fc region of rabbit immunoglobulin. These reagents, which collectively recognize all forms of ADPR with different specificities, are useful in a broad array of antibody-based assays, such as immunoblotting, immunofluorescent staining of cells, and immunoprecipitation. Observations from these assays suggest that the biology of ADPR is more diverse, rich, and complex than previously thought. The ARBD-Fc fusion proteins described herein will be useful tools for future exploration of the chemistry, biochemistry, and biology of ADP-ribose.