SUMO targeting of a stress-tolerant Ulp1 SUMO protease

Determination of enzyme kinetic parameters of fast-acting Schizosaccharomyces pombe Ulp1 catalytic domain using Forster resonance energy transfer (FRET) assay

The SUMO fusion technology has immensely contributed to the soluble production of therapeutics and other recombinant proteins in E. coli. The structure-based functionality of SUMO protease has remained the primary determinant for choosing SUMO as a solubility enhancer tag. This study details the quantification of kinetic parameters of commercially relevant S. pombe Ulp1 catalytic domain by employing a Forster resonance energy transfer (FRET) based assay. The energy transfer between the fluorophores allowed to elucidate the kinetic parameters precisely. For the FRET assay, the ECFP-SpSUMO-EYFP construct was successfully cloned in the pET28a vector. The fusion protein was efficaciously expressed and purified near homogeneity. The assay employed provided a real-time investigation of SpUlp1 catalysis. The enzyme turnover number (kcat) was computed as 9.08 s-1. The Michaelis-Menten constant, KM was determined as 0.65 × 101 μM with a maximum velocity (Vmax) of 0.045 μM/s. The substrate specificity ratio, kcat/KM was calculated to be 1.39 × 106 M-1 s-1. Using the FRET assay approach, the fast-acting nature of the SpUlp1 was analyzed in real-time at even 103 times higher molar substrate concentration. Thus, the kinetics of commercially relevant SpUlp1 was successfully demonstrated along with its large-scale production at 50 L bioreactor, where the maximum product concentration was 4.8 g/L. Additionally, the S. pombe SUMO used in the current study could potentially replace the S. cerevisiae SUMO as a solubility enhancer fusion tag.

Mechanisms underlining Kelp (Saccharina japonica) adaptation to relative high seawater temperature

Saccharina japonica has been cultivated in China for almost a century. From Dalian to Fujian, the lowest and the highest seawater temperatures in the period of cultivation increased by 14℃ and 8℃, respectively. Its adaptation to elevated seawater temperature is an example of securing the natural habitats of a species. To decipher the mechanisms underlining S. japonica adaptation to relative high seawater temperature, we assembled ~ 516.3 Mb female gametophyte genome and ~ 540.3 Mb of the male, respectively. The gametophytes isolated from southern China kelp cultivars acclimated to the relative high seawater temperature by transforming amino acids, glycosylating protein, maintaining osmotic pressure, intensifying the innate immune system, and exhausting energy and reduction power through the PEP-pyruvate-oxaloacetate node and the iodine cycle. They adapted to the relative high seawater temperature by transforming amino acids, changing sugar metabolism and intensifying innate immune system. The sex of S. japonica was determined by HMG-sex, and around this male gametophyte determiner the stress tolerant genes become linked to or associated with.

Protein Modification Employing Non-Canonical Amino Acids to Prepare SUMOylation Detecting Bioconjugates

Protein modification with non-canonical amino acids (ncAAs) represents a useful technology to afford homogenous samples of bioconjugates with site-specific modification. This technique can be directly applied to the detection of aberrant SUMOylation patterns, which are often indicative of disease states. Modified SUMO-trapping proteins, consisting of a catalytically inactive ULP1 fragment (UTAG) fused to the maltose-binding protein MBP, are useful reagents for the binding and labeling of SUMOylated proteins. Mutation of this UTAG fusion protein to facilitate amber suppression technologies for the genetic incorporation of ncAAs was assessed to provide a functional handle for modification. Ultimately, two sites in the maltose-binding protein (MBP) fusion were identified as ideal for incorporation and bioconjugation without perturbation to the SUMO-trapping ability of the UTAG protein. This functionality was then employed to label SUMOylated proteins in HeLa cells and demonstrate their enrichment in the nucleus. This modified UTAG-MBP-ncAA protein has far-reaching applications for both diagnostics and therapeutics.

The Role of Protein SUMOylation in Human Hepatocellular Carcinoma: A Potential Target of New Drug Discovery and Development

Small ubiquitin-like modifier (SUMO) is a highly conserved post-translational modification protein, mainly found in eukaryotes. They are widely expressed in different tissues, including the liver. As an essential post-translational modification, SUMOylation is involved in many necessary regulations in cells. It plays a vital role in DNA repair, transcription regulation, protein stability and cell cycle progression. Increasing shreds of evidence show that SUMOylation is closely related to Hepatocellular carcinoma (HCC). The high expression of SUMOs in the inflammatory hepatic tissue may lead to the carcinogenesis of HCC. At the same time, SUMOs will upregulate the proliferation and survival of HCC, migration, invasion and metastasis of HCC, tumour microenvironment as well as drug resistance. This study reviewed the role of SUMOylation in liver cancer. In addition, it also discussed natural compounds that modulate SUMO and target SUMO drugs in clinical trials. Considering the critical role of SUMO protein in the occurrence of HCC, the drug regulation of SUMOylation may become a potential target for treatment, prognostic monitoring and adjuvant chemotherapy of HCC.

Detection of rapidly accumulating stress-induced SUMO in prostate cancer cells by a fluorescent SUMO biosensor

SUMO conjugates and SUMO chains form when SUMO, a small ubiquitin-like modifier protein, is covalently linked to other cellular proteins or itself. During unperturbed growth, cells maintain balanced levels of SUMO conjugates. In contrast, eukaryotic cells that are exposed to proteotoxic and genotoxic insults mount a cytoprotective SUMO stress response (SSR). One hallmark of the SSR is a rapid and massive increase of SUMO conjugates in response to oxidative, thermal, and osmotic stress. Here, we use a recombinant fluorescent SUMO biosensor, KmUTAG-fl, to investigate differences in the SSR in a normal human prostate epithelial cell line immortalized with SV40 (PNT2) and two human prostate cancer cell lines that differ in aggressiveness and response to androgen (LNCaP and PC3). In cells that grow unperturbed, SUMO is enriched in the nuclei of all three cell lines. However, upon 30 min of exposure to ultraviolet radiation or oxidative stress, we detected significant cytosolic enrichment of SUMO as measured by KmUTAG-fl staining. This rapid enrichment in cytosolic SUMO levels was on average fivefold higher in the LNCaP and PC3 prostate cancer cell lines compared to normal immortalized PNT2 cells. Additionally, this enhanced enrichment of cytosolic SUMO was reversible as cells recovered from stress exposure. Our study validates the use of the fluorescent KmUTAG-fl SUMO biosensor to detect differences of SUMO levels and localization between normal and cancer cells and provides new evidence that cancer cells may exhibit an enhanced SSR.

Ginkgolic Acid Rescues Lens Epithelial Cells from Injury Caused by Redox Regulated-Aberrant Sumoylation Signaling by Reviving Prdx6 and Sp1 Expression and Activities

Sumoylation is a downstream effector of aging/oxidative stress; excess oxidative stress leads to dysregulation of a specificity protein1 (Sp1) and its target genes, such as Peroxiredoxin 6 (Prdx6), resulting in cellular damage. To cope with oxidative stress, cells rely on a signaling pathway involving redox-sensitive genes. Herein, we examined the therapeutic efficacy of the small molecule Ginkgolic acid (GA), a Sumoylation antagonist, to disrupt aberrant Sumoylation signaling in human and mouse lens epithelial cells (LECs) facing oxidative stress or aberrantly expressing Sumo1 (small ubiquitin-like modifier). We found that GA globally reduced aberrant Sumoylation of proteins. In contrast, Betulinic acid (BA), a Sumoylation agonist, augmented the process. GA increased Sp1 and Prdx6 expression by disrupting the Sumoylation signaling, while BA repressed the expression of both molecules. In vitro DNA binding, transactivation, Sumoylation and expression assays revealed that GA enhanced Sp1 binding to GC-boxes in the Prdx6 promoter and upregulated its transcription. Cell viability and intracellular redox status assays showed that LECs pretreated with GA gained resistance against oxidative stress-driven aberrant Sumoylation signaling. Overall, our study revealed an unprecedented role for GA in LECs and provided new mechanistic insights into the use of GA in rescuing LECs from aging/oxidative stress-evoked dysregulation of Sp1/Prdx6 protective molecules.