An in vitro Förster resonance energy transfer-based high-throughput screening assay identifies inhibitors of SUMOylation E2 Ubc9.

SUMOylation is one of the posttranslational modifications that mediate cellular activities such as transcription, DNA repair, and signal transduction and is involved in the cell cycle. However, only a limited number of small molecule inhibitors have been identified to study its role in cellular processes. Here, we report a Förster resonance energy transfer (FRET) high-throughput screening assay based on the interaction between E2 Ubc9 and E3 PIAS1. Of the 3200 compounds screened, 34 (1.1%) showed higher than 50% inhibition and 4 displayed dose-response inhibitory effects. By combining this method with a label-free surface plasmon resonance (SPR) assay, false positives were excluded leading to discovering WNN0605-F008 and WNN1062-D002 that bound to Ubc9 with KD values of 1.93 ± 0.62 and 5.24 ± 3.73 µM, respectively. We examined the effect of the two compounds on SUMO2-mediated SUMOylation of RanGAP1, only WNN0605-F008 significantly inhibited RanGAP1 SUMOylation, whereas WNN1062-D002 did not show any inhibition. These compounds, with novel chemical scaffolds, may serve as the initial material for developing new SUMOylation inhibitors.

Local monitoring of SARS-CoV-2 variants in two large California counties in 2021.

Coronavirus Disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), continues to persist due to mutations resulting in newer, more infectious variants of concern. We aimed to leverage an ongoing private SARS-CoV-2 testing laboratory's infrastructure to monitor SARS-CoV-2 variants in two large California counties. Study enrollment was offered to adults aged 18 years or older in Los Angeles County and Riverside County who recently tested positive for SARS-CoV-2 with a polymerase chain reaction (PCR) assay. A cycle threshold value less than or equal to 30 cycles was considered a positive test for sequencing purposes. Within 5 days of study enrollment, clinician-monitored, self-collected oral fluid and anterior nares swab specimens were obtained from participants. Specimens were transported and stored at 8 °C or cooler. Samples underwent ribonucleic acid extraction, library preparation, and sequencing. SARS-CoV-2 lineages were identified using sequencing data. Participant and genomic data were analyzed using statistical tools and visualized with toolkits. The study was approved by Advarra Institutional Review Board (Pro00053729). From May 27, 2021 to September 9, 2021, 503 individuals were enrolled and underwent specimen collection. Of the 503 participants, 238 (47.3%) participants were women, 329 (63.6%) participants were vaccinated, and 221 (43.9%) participants were of Hispanic or Spanish origin. Of the cohort, 496 (98.6%) participants had symptoms at the time of collection. Among the 503 samples, 443 (88.1%) nasal specimens and 353 (70.2%) oral specimens yielded positive sequencing results. Over our study period, the prevalence of the Alpha variant of SARS-CoV-2 decreased (initially 23.1% [95% confidence interval (95% CI): 0-0.49%] to 0% [95% CI 0.0-0.0%]) as the prevalence of the Delta variant of SARS-CoV-2 increased (initially 33.3% [95% CI 0.0-100.0%] to 100.0% [95% CI 100.0-100.0%]). A strain that carried mutations of both Delta and Mu was identified. We found that outpatient SARS-CoV-2 variant surveillance could be conducted in a timely and accurate manner. The prevalence of different variants changed over time. A higher proportion of nasal specimens yielded results versus oral specimens. Timely and regional outpatient SARS-CoV-2 variant surveillance could be used for public health efforts to identify changes in SARS-CoV-2 strain epidemiology.

Target Virus or Target Ourselves for COVID-19 Drugs Discovery?-Lessons learned from anti-influenza virus therapies.

The COVID-19 pandemic, after it was reported in December 2019, is a highly contagious and now spreading to over 190 countries, causing a severe public health burden. Currently, there is no vaccine or specific drug to treat COVID-19, which is caused by a novel coronavirus, SARS-2-CoV. For this emergency, the FDA has approved Remdesivir and Hydroxychloroquine for treatment of COVID-19 as Emergency Use Authorization. However, even after this pandemic, COVID-19 may still have a chance to come back. Therefore, we need to come out with new strategies for drug discovery for combating COVID-19 in the future.

A novel SUMOylation site in the influenza a virus NS1 protein identified with a highly sensitive FRET assay.

Nonstructural protein 1 (NS1) of the influenza A virus is a major contributor to the virulence of the seasonal influenza A viruses, in part because it interferes with host viral defense mechanisms. SUMOylation regulates NS1 activity, and several residues of NS1 have been identified with traditional biochemical approaches as acceptor sites for SUMOylation. In this study, we developed a novel FRET assay to assess SUMOylation. Using this assay, we demonstrated that the lysine residue K131 in the effector domain of NS1 is a previously unidentified SUMO acceptor site. A recombinant H1N1 influenza A virus (A/PR/8/34) expressing a K131 SUMOylation-deficient NS1 had a significantly lower growth rate than the wild-type virus. These results suggest that NS1 SUMOylation at K131 is required for the rapid replication of H1N1 influenza viruses. The interaction between the NS1 protein and the host SUMOylation components may serve as a novel target for the development of anti-influenza A drugs.

Specific substrate recognition and thioester intermediate determinations in ubiquitin and SUMO conjugation cascades revealed by a high-sensitive FRET assay.

Ubiquitin and ubiquitin-like proteins (Ubls), such as SUMO, are covalently conjugated to their targets by related, but distinct enzymatic conjugation reactions that involve the dynamic E1-E2-E3 enzyme cascade. E1s activate Ubls by catalyzing Ubl C-terminal adenylation, with the help of ATP, to form a covalent thioester bond. Subsequently, Ubls are transferred to E2 to generate a thioester-linked product. In previous studies, we showed the dynamic processes and thioester intermediates of SUMO with its E1 and E2 conjugating enzymes. Studies of the enzyme specificity of the Ubl conjugation cascade are normally carried out by tedious biochemical processes, and the reaction intermediates are often difficult to capture because they are unstable and have short half-lives. Here, using our recently developed robust quantitative FRET-based technology, we describe systematic investigations of enzymatic specificity and thioester intermediate determination of ubiquitin with its E1-E2 ligases in conjugation with SUMO and its ligases. Our technology easily determined the strong specificity of enzyme-substrate interactions and thioester intermediates in ubiquitination and SUMOylation cascades. The traditional FRET pair ECFP/EYFP lacked adequate signals for these assays. However, in contrast, the highly sensitive FRET pair CyPet/YPet was easily harnessed to define the reaction specificities and intermediates. In addition, the thioester intermediates can be readily monitored by a newly defined FRET index parameter. These results provide an example of a systems biology approach to determine Ubl conjugation specificity and demonstrate that a robust FRET technology can be used to identify enzymes and substrates in other Ubl pathways.