Tuning Iron Active Sites of FeOOH via Al3+ and Heteroatom Doping-Induced Asymmetric Oxygen Vacancy Electronic Structure for Efficient Alkaline Water Splitting.

Oxygen evolution reaction is the essential anodic reaction for water splitting. Designing tunable electronic structures to overcome its slow kinetics is an effective strategy. Herein, the molecular ammonium iron sulfate dodecahydrate is employed as the precursor to synthesize the C, N, S triatomic co-doped Fe(Al)OOH on Ni foam (C,N,S-Fe(Al)OOH-NF) with asymmetric electronic structure. Both in situ oxygen vacancies and their special electronic configuration enable the electron transfer between the d-p orbitals and get the increase of OER activity. Density functional theory calculation further indicates the effect of electronic structure on catalytic activity and stability at the oxygen vacancies. In alkaline solution, the catalyst C,N,S-Fe(Al)OOH-NF shows good catalytic activity and stability for water splitting. For OER, the overpotential of 10 mA cm-2 is 264 mV, the tafel slope is 46.4 mV dec-1, the HER overpotential of 10 mA cm-2 is 188 mV, the tafel slope is 59.3 mV dec-1. The stability of the catalyst can maintain ≈100 h. This work has extraordinary implications for understanding the mechanistic relationship between electronic structure and catalytic activity for designing friendly metal (oxy)hydroxide catalysts.

Continuous Ultrathin Zwitterionic Covalent Organic Framework Membrane Via Surface-Initiated Polymerization Toward Superior Water Retention.

Efficient construction of proton transport channels in proton exchange membranes maintaining conductivity under varied humidity is critical for the development of fuel cells. Covalent organic frameworks (COFs) hold great potential in providing precise and fast ion transport channels. However, the preparation of continuous free-standing COF membranes retaining their inherent structural advantages to realize excellent proton conduction performance is a major challenge. Herein, a zwitterionic COF material bearing positive ammonium ions and negative sulphonic acid ions is developed. Free-standing COF membrane with adjustable thickness is constructed via surface-initiated polymerization of COF monomers. The porosity, continuity, and stability of the membranes are demonstrated via the transmission electron microscopy (TEM), atomic force microscopy (AFM), and scanning electron microscopy (SEM) characterization. The rigidity of the COF structure avoids swelling in aqueous solution, which improves the chemical stability of the proton exchange membranes and improves the performance stability. In the higher humidity range (50-90%), the prepared zwitterionic COF membrane exhibits superior capability in retaining the conductivity compared to COF membrane merely bearing sulphonic acid group. The established strategy shows the potential for the application of zwitterionic COF in the proton exchange membrane fuel cells.

Synthesis of {AlMo14O44}-Based Supramolecular Structures with High Proton Conductivity.

Polyoxometalates (POMs) are esteemed for their remarkable stability and exceptionally high proton conductivity, rendering them ripe for extensive exploration owing to their research significance. Herein, we synthesized two bimolybdenum-capped {AlMoVI8MoV6O44} cluster-based coordination polymers through a solvothermal method. Single-crystal X-ray diffraction analysis elucidates that H[(H2bimb)3(AlMoVI8MoV6O44)] [bimb = 1,4-bis(imidazole-1-ylmethyl)benzene, compound 1] is the POMs-organic supramolecular structure. The introduction of zinc ions into the reaction environment facilitated the connection of initially dispersed ligands, which yielded the well-ordered structure H3[Zn2(bimb)4(AlMoVI8MoV6O44)]·4H2O (compound 2) with a layer distance of 11.8 Å. The proton conductivities (σ) of two compounds were measured under conditions of 85 °C and 98% relative humidity (RH), resulting in values of 3.89 × 10-2 and 4.76 × 10-2 S·cm-1, respectively. This study presents a novel approach to fabricating POMs as proton conductors through structural design and manufacturing adjustments.

Genetic and pharmacological inhibition of GRPR protects against acute kidney injury via attenuating renal inflammation and necroptosis.

Gastrin-releasing peptide (GRP) binds to its receptor (GRP receptor [GRPR]) to regulate multiple biological processes, but the function of GRP/GRPR axis in acute kidney injury (AKI) remains unknown. In the present study, GRPR is highly expressed by tubular epithelial cells (TECs) in patients or mice with AKI, while histone deacetylase 8 may lead to the transcriptional activation of GRPR. Functionally, we uncovered that GRPR was pathogenic in AKI, as genetic deletion of GRPR was able to protect mice from cisplatin- and ischemia-induced AKI. This was further confirmed by specifically deleting the GRPR gene from TECs in GRPRFlox/Flox//KspCre mice. Mechanistically, we uncovered that GRPR was able to interact with Toll-like receptor 4 to activate STAT1 that bound the promoter of MLKL and CCL2 to induce TEC necroptosis, necroinflammation, and macrophages recruitment. This was further confirmed by overexpressing STAT1 to restore renal injury in GRPRFlox/Flox/KspCre mice. Concurrently, STAT1 induced GRP synthesis to enforce the GRP/GRPR/STAT1 positive feedback loop. Importantly, targeting GRPR by lentivirus-packaged small hairpin RNA or by treatment with a novel GRPR antagonist RH-1402 was able to inhibit cisplatin-induced AKI. In conclusion, GRPR is pathogenic in AKI and mediates AKI via the STAT1-dependent mechanism. Thus, targeting GRPR may be a novel therapeutic strategy for AKI.

DTX3L Accelerates Pancreatic cancer Progression via FAK/PI3K/AKT Axis.

DTX3L (Deltex E3 ubiquitin ligase 3 L) is an E3 ubiquitin ligase, a member of the deltex family. It is also known as B-lymphoma and BAL-associated protein (BBAP). DTX3L has been proven to play an important role in various tumor development; however, its role in pancreatic cancer remains unknown. So, we analyzed the DTX3L expression in pancreatic cancer based on the TCGA database and verified it in our samples by qRT­PCR and western blot. We identified that DTX3L was highly expressed in pancreatic cancer, and its expression level was significantly negatively correlated with patients' survival. Using CCK8, colony formation, transwell, and wound healing assays, we found that upregulated DTX3L promotes pancreatic cancer cell proliferation, invasion, and migration. Mechanically, DTX3L combined with EGFR (epidermal growth factor receptor) and prevented the ubiquitination degradation of it. Upregulated EGFR activated the FAK/PI3K/Akt pathway and promoted the progression of pancreatic cancer. Moreover, we found that DTX3L can weaken pancreatic cancer cells' sensitivity to chemotherapy using the orthotopic implant tumor model. In conclusion, DTX3L accelerates pancreatic cancer progression by EGFR dependent FAK/PI3K/Akt pathway activation and may become a potential target for pancreatic cancer treatment.

Ultrathin Free-Standing Porous Aromatic Framework Membranes for Efficient Anion Transport.

Porous aromatic frameworks (PAFs) show promising potential in anionic conduction due to their high stability and customizable functionality. However, the insolubility of most PAFs presents a significant challenge in their processing into membranes and subsequent applications. In this study, continuous PAF membranes with adjustable thickness were successfully created using liquid-solid interfacial polymerization. The rigid backbone and the stable C-C coupling endow PAF membrane with superior chemical and dimensional stabilities over most conventional polymer membranes. Different quaternary ammonium functionalities were anchored to the backbone through flexible alkyl chains with tunable length. The optimal PAF membrane exhibited an OH- conductivity of 356.6 mS ⋅ cm-1 at 80 °C and 98 % relative humidity. Additionally, the PAF membrane exhibited outstanding alkaline stability, retaining 95 % of its OH- conductivity after 1000 hours in 1 M NaOH. To the best of our knowledge, this is the first application of PAF materials in anion exchange membranes, achieving the highest OH- conductivity and exceptional chemical/dimensional stability. This work provides the possibility for the potential of PAF materials in anionic conductive membranes.

Multi-Template-Guided Synthesis of High-Dimensional Molecular Assemblies for Humidity Gradient-Based Power Generators.

Systematically orchestrating fundamental building blocks into intricate high-dimensional molecular assemblies at molecular level is imperative for multifunctionality integration. However, this remains a formidable task in crystal engineering due to the dynamic nature of inorganic building blocks. Herein, we develop a multi-template-guided strategy to control building blocks. The coordination modes of ligands and the spatial hindrance of anionic templates are pivotal in dictating the overall structures. Flexible multi-dentate linkers selectively promote the formation of oligomeric assembly ([TeO3(Mo2O2S2)3O2(OH)(C5O2H7)3]4- {TeMo6}) into tetrahedral cages ([(TeO3)4(Mo2O2S2)12(OH)12(C9H9O4P)6]8- {Te4Mo24} and [(AsO4)4(Mo2O2S2)12(OH)12(C9H9O6)4]12- {As4Mo24}), while steric hindrance from anionic templates further assists in assembling cages into an open quadruply twisted Möbius nanobelt ([(C6H5O3P)8(Mo2O2S2)24(OH)24(C8H10O4)12]16- {P8Mo48}). Among these structures, the hydrophilic-hydrophobic hybrid cage {Te4Mo24} emerges as an exemplary molecular model for proton conduction and serves as a prototype for humidity gradient-based power generators (HGPGs). The Te4Mo24-PVDF-based HGPG (PVDF=Poly(vinylidene fluoride)) exhibits notable stability and power generation, yielding an open-circuit voltage of 0.51 V and a current density of 77.8 nA cm-2 at room temperature and 90 % relative humidity (RH). Further insights into the interactions between water molecules and microscale molecules within the generator are achieved through molecular dynamics simulations. This endeavor unveils a universal strategy for synthesizing multifunctional integration molecules.

Controllable Transition Metal-Directed Assembly of [Mo2O2S2]2+ Building Blocks into Smart Molecular Humidity-Responsive Actuators.

Smart molecular actuators have become a cutting-edge theme due to their ability to convert chemical energy into mechanical energy under external stimulations. However, realizing actuation at the molecular level and elucidating the mechanisms for actuating still remain challenging. Herein, we design and fabricate a novel nanoscaled polyoxometalate-based humidity-responsive molecular actuator {Bi8Mo48} through the assembly of [Mo2O2S2]2+ units, transition metals, and flexible phosphonic acid ligands. {Bi8Mo48} exhibits a semi-flexible cage-like architecture with oxygen-rich surfaces and highly negative charges 72-. The nanoscaled molecular actuator shows reversible expansion and contraction behavior under humidity variations due to lattice expansion and contraction induced by hydrogen bonding and solvation interactions between {Bi8Mo48} and water molecules. Molecular dynamics simulation was further employed to study these processes, which provides a fundamental understanding for the mechanism of humidity actuation at the molecular level.

Synthesis of Phosphovanadate-Based Porous Inorganic Frameworks with High Proton Conductivity.

Materials with high proton conductivity have attracted significant attention for their wide-ranging applications in proton exchange membrane fuel cells. However, the design of new and efficient porous proton-conducting materials remains a challenging task. The structure-controllable and highly stable metal phosphates can be synthesized into layer or frame networks to provide proton transport capabilities. Herein, we have successfully synthesized three isomorphic metal phosphovanadates, namely, H2(C2H10N2)2[MII(H2O)2(VIVO)8(OH)4(PO4)4(HPO4)4] (C2H8N2 = 1,2-ethylenediamine; M = Co, Ni, and Cu), by the hydrothermal method employing ethylenediamine as a template. These pure inorganic open frameworks exhibit a cavity width ranging from 6.4 to 7.5 Å. Remarkably, the proton conductivity of compounds 1-3 can reach 1 × 10-2 S·cm-1 at 85 °C and 97% relative humidity (RH), and they can remain stable at high temperatures as well as long-term stability. This work provides a novel strategy for the development and design of porous proton-conducting materials.

A compensation mechanism for air pollutants generated by tourism-related land-based transportation: An exergy-based case study from Macao.

This paper discusses the compensation standard for exhaust pollution and devises a compensation mechanism for Macao's tourism-related transport sector based on an integration of chemical exergy and universal exergy, using data on gasoline consumption by automobile sector retrieved from the transportation industry. The results reveal that: (1) the exergy values of air pollutant emissions increased from 1.53 × 1012 kJ in 2010 to 2.03 × 1012 kJ in 2019 (an increase of 1.33 times), and the exergy of CO, NOx, and SO2 emissions accounted for 77.5%, 20.4% and 2.1% of total exhaust emissions in Macao respectively. (2) In 2019, the monetary value of emission exergy, and the environmental costs of air pollution, were 1.7 times greater than in 2010. (3) If Light Rail Transit is compensated for, then the mean interval's values of the upper and lower limits of the compensation standard are 0.55 USD and 0.05 USD, respectively. When gasoline tax is used as a means of compensation it is necessary to raise its rate by about 8% based on the tax rate. A three-stage bargaining game model is used to provide evidence that this compensation standard is practical and acceptable.

Constructing Oxygen Vacancies via Engineering Heterostructured Fe3 C/Fe3 O4 Catalysts for Electrochemical Ammonia Synthesis.

Electrocatalytic nitrogen reduction reaction (NRR) under ambient conditions provides an intriguing pathway to convert N2 into NH3 . However, significant kinetic barriers of the NRR at low temperatures in desirable aqueous electrolytes remain a grand challenge due to the inert N≡N bond of the N2 molecule. Herein, we propose a unique strategy for in situ oxygen vacancy construction to address the significant trade-off between N2 adsorption and NH3 desorption by building a hollow shell structured Fe3 C/Fe3 O4 heterojunction coated with carbon frameworks (Fe3 C/Fe3 O4 @C). In the heterostructure, the Fe3 C triggers the oxygen vacancies of the Fe3 O4 component, which are likely active sites for the NRR. The design could optimize the adsorption strength of the N2 and Nx Hy intermediates, thus boosting the catalytic activity for the NRR. This work highlights the significance of the interaction between defect and interface engineering for regulating electrocatalytic properties of heterostructured catalysts for the challenging NRR. It could motivate an in-depth exploration to advance N2 reduction to ammonia.

Designed Tetranuclear Iron-oxo Clusters with Redox Activity for High-Performance Lithium Storage.

Polyoxometalates (POMs) are considered as promising catalysts with unique redox activity at the molecular level for energy storage. However, eco-friendly iron-oxo clusters with special metal coordination structures have rarely been reported for Li-ion storage. Herein, three novel redox-active tetranuclear iron-oxo clusters have been synthesized using the solvothermal method with different ratios of Fe3+ and SO4 2- . Further, they can serve as anode materials for Li-ion batteries. Among them, cluster H6 [Fe4 O2 (H2 O)2 (SO4 )7 ]⋅H2 O, the stable structure extended by SO4 2- with a unique 1D pore, displays a specific discharge capacity of 1784 mAh g-1 at 0.2 C and good cycle performance (at 0.2 C and 4 C). This is the first instance of inorganic iron-oxo clusters being used for Li-ion storage. Our findings present a new molecular model system with a well-defined structure and offer new design concepts for the practical application of studying the multi-electron redox activity of iron-oxo clusters.

Insulin-like growth factor binding protein 7 promotes acute kidney injury by alleviating poly ADP ribose polymerase 1 degradation.

The novel biomarker, insulin-like growth factor binding protein 7 (IGFBP7), is used clinically to predict different types of acute kidney injury (AKI) and has drawn significant attention as a urinary biomarker. However, as a secreted protein in the circulation of patients with AKI, it is unclear whether IGFBP7 acts as a key regulator in AKI progression, and if mechanisms underlying its upregulation still need to be determined. Here we found that IGFBP7 is highly expressed in the blood and urine of patients and mice with AKI, possibly via a c-Jun-dependent mechanism, and is positively correlated with kidney dysfunction. Global knockout of IGFBP7 ameliorated kidney dysfunction, inflammatory responses, and programmed cell death in murine models of cisplatin-, kidney ischemia/reperfusion-, and lipopolysaccharide-induced AKI. IGFBP7 mainly originated from kidney tubular epithelial cells. Conditional knockout of IGFBP7 from the kidney protected against AKI. By contrast, rescue of IGFBP7 expression in IGFBP7-knockout mice restored kidney damage and inflammation. IGFBP7 function was determined in vitro using recombinant IGFBP7 protein, IGFBP7 knockdown, or overexpression. Additionally, IGFBP7 was found to bind to poly [ADP-ribose] polymerase 1 (PARP1) and inhibit its degradation by antagonizing the E3 ubiquitin ligase ring finger protein 4 (RNF4). Thus, IGFBP7 in circulation acts as a biomarker and key mediator of AKI by inhibiting RNF4/PARP1-mediated tubular injury and inflammation. Hence, over-activation of the IGFBP7/PARP1 axis represents a promising target for AKI treatment.

Space-Confined Nucleation of Semimetal-Oxo Clusters within a [H7P8W48O184]33- Macrocycle: Synthesis, Structure, and Enhanced Proton Conductivity.

Spatially confined assembly of semimetallic oxyanions (AsO33- and SbO33-) within a [H7P8W48O184]33- (P8W48) macrocycle has afforded three nanoscale polyanions, [{AsIII5O4(OH)3}2(P8W48O184)]32- (As10), [(SbIIIOH)4(P8W48O184)]32- (Sb4), and [(SbIIIOH)8(P8W48O184)]24- (Sb8), which were crystallized as the hydrated mixed-cation salts (Me2NH2)13K7Na2Li10[{AsIII5O4(OH)3}2(P8W48O184)]·32H2O (DMA-KNaLi-As10), K20Li12[(SbIIIOH)4(P8W48O184)]·52H2O (KLi-Sb4), and (Me2NH2)8K6Na5Li5[(SbIIIOH)8(P8W48O184)]·65H2O (DMA-KNaLi-Sb8), respectively. A multitude of solid- and solution-state physicochemical techniques were employed to systematically characterize the structure and composition of the as-made compounds. The polyanion of As10 represents the first example of a semimetal-oxo cluster-substituted P8W48 and accommodates the largest AsIII-oxo cluster in polyoxometalates (POMs) reported to date. The number of incorporated SbO33- groups in Sb4 and Sb8 could be customized by a simple variation of SbIII-containing precursors. Encapsulation of semimetallic oxyanions inside P8W48 sets out a valid strategy not only for the development of host-guest assemblies in POM chemistry but also for their function expansion in emerging applications such as proton-conducting materials, for which DMA-KNaLi-As10 showcases an outstanding conductivity of 1.2 × 10-2 S cm-1 at 85 °C and 70% RH.

Stratifin promotes renal dysfunction in ischemic and nephrotoxic AKI mouse models via enhancing RIPK3-mediated necroptosis.

Stratifin (SFN) is a member of the 14-3-3 family of highly conserved soluble acidic proteins, which regulates a variety of cellular activities such as cell cycle, cell growth and development, cell survival and death, and gene transcription. Acute kidney injury (AKI) is prevalent disorder characterized by inflammatory response, oxidative stress, and programmed cell death in renal tubular epithelial cells, but there is still a lack of effective therapeutic target for AKI. In this study, we investigated the role of SFN in AKI and the underlying mechanisms. We established ischemic and nephrotoxic AKI mouse models caused by ischemia-reperfusion (I/R) and cisplatin, respectively. We conducted proteomic and immunohistochemical analyses and found that SFN expression levels were significantly increased in AKI patients, cisplatin- or I/R-induced AKI mice. In cisplatin- or hypoxia/reoxygenation (H/R)-treated human proximal tubule epithelial cells (HK2), we showed that knockdown of SFN significantly reduced the expression of kidney injury marker Kim-1, attenuated programmed cell death and inflammatory response. Knockdown of SFN also significantly alleviated the decline of renal function and histological damage in cisplatin-caused AKI mice in vivo. We further revealed that SFN bound to RIPK3, a key signaling modulator in necroptosis, to induce necroptosis and the subsequent inflammation in cisplatin- or H/R-treated HK2 cells. Overexpression of SFN increased Kim-1 protein levels in cisplatin-treated MTEC cells, which was suppressed by RIPK3 knockout. Taken together, our results demonstrate that SFN that enhances cisplatin- or I/R-caused programmed cell death and inflammation via interacting with RIPK3 may serve as a promising therapeutic target for AKI treatment.

Molecular Iron Oxide Clusters Boost the Oxygen Reduction Reaction of Platinum Electrocatalysts at Near-Neutral pH.

The oxygen reduction reaction (ORR) is a key energy conversion process, which is critical for the efficient operation of fuel cells and metal-air batteries. Here, we report the significant enhancement of the ORR-performance of commercial platinum-on-carbon electrocatalysts when operated in aqueous electrolyte solutions (pH 5.6), containing the polyoxoanion [Fe28 (µ3 -O)8 (L-(-)-tart)16 (CH3 COO)24 ]20- . Mechanistic studies provide initial insights into the performance-improving role of the iron oxide cluster during ORR. Technological deployment of the system is demonstrated by incorporation into a direct formate microfluidic fuel cell (DFMFC), where major performance increases are observed when compared with reference electrolytes. The study provides the first examples of iron oxide clusters in electrochemical energy conversion and storage.

Surface-Mediated Construction of an Ultrathin Free-Standing Covalent Organic Framework Membrane for Efficient Proton Conduction.

As a new class of crystalline porous organic materials, covalent organic frameworks (COFs) have attracted considerable attention for proton conduction owing to their regular channels and tailored functionality. However, most COFs are insoluble and unprocessable, which makes membrane preparation for practical use a challenge. In this study, we used surface-initiated condensation polymerization of a trialdehyde and a phenylenediamine for the synthesis of sulfonic COF (SCOF) coatings. The COF layer thickness could be finely tuned from 10 to 100 nm by controlling the polymerization time. Moreover, free-standing COF membranes were obtained by sacrificing the bridging layer without any decomposition of the COF structure. Benefiting from the abundant sulfonic acid groups in the COF channels, the proton conductivity of the SCOF membrane reached 0.54 S cm-1 at 80 °C in pure water. To our knowledge, this is one of the highest values for a pristine COF membrane in the absence of additional additives.

Precise Molecular-Level Modification of Nafion with Bismuth Oxide Clusters for High-performance Proton-Exchange Membranes.

Fabricating proton exchange membranes (PEMs) with high ionic conductivity and ideal mechanical robustness through regulation of the membrane microstructures achieved by molecular-level hybridization remains essential but challenging for the further development of high-performance PEM fuel cells. In this work, by precisely hybridizing nano-scaled bismuth oxide clusters into Nafion, we have fabricated the high-performance hybrid membrane, Nafion-Bi12 -3 %, which showed a proton conductivity of 386 mS cm-1 at 80 °C in aqueous solution with low methanol permeability, and conserved the ideal mechanical and chemical stabilities as PEMs. Moreover, molecular dynamics (MD) simulation was employed to clarify the structural properties and the assembly mechanisms of the hybrid membrane on the molecular level. The maximum current density and power density of Nafion-Bi12 -3 % for direct methanol fuel cells reached to 432.7 mA cm-2 and 110.2 mW cm-2 , respectively. This work provides new insights into the design of versatile functional polymer electrolyte membranes through polyoxometalate hybridization.

The E3 ligase for metastasis associated 1 protein, TRIM25, is targeted by microRNA-873 in hepatocellular carcinoma.

Tumor metastasis accounts for 90% of all cancer-related deaths. Epithelial to mesenchymal transition (EMT) considered to be centrally important in acquired resistance to chemotherapy and in progression of tumors to secondary organs. One of the important mediators of metastatic progression in hepatocellular carcinoma (HCC) is the metastasis associated protein 1 (MTA-1). We have earlier shown that in the context of HCC and normal liver cell lines, MTA-1 protein is actively stabilized in HCC cell lines and actively degraded in normal liver cells. We have also shown that TRIM25 is the E3 ligase that interacts with and degrades MTA-1 protein. The identity of the factor regulating expression of TRIM25 in normal liver cells and HCC is unknown. In the current work we elucidate that microRNA (miR)- 873 targets TRIM25 in HCC cells. Both metagenomic analysis and quantification of miR-873 and TRIM25 in 25 HCC patients revealed an inverse correlation between the two in HCC patients with high miR-873 and low TRIM25 expression, respectively. The expression pattern was mimicked in the normal liver cells THLE-2 and the HCC cell line, HuH6. In vitro luciferase reporter assays confirmed TRIM25 as the target of miR-873. Transient transfection of HuH6 cells with an anti-miR-873 antagomir significantly decreased both transwell motility in these cells. Furthermore, in in vivo xenograft assays treatment with anti-miR-873 antagomir significantly decreased hepatic nodules formation. Cumulatively, our data indicate that suppression of TRIM25 expression by high levels of miR-873 dictates MTA1 protein upregulation in HCC.

Mechanism of TRIM25 mediated ubiquitination of metastasis associated protein (MTA) 1 in normal liver cells.

Ninety percent of all cancer related deaths happen due to metastatic progression. One important protein facilitating metastatic progression in hepatocellular carcinoma (HCC) is the metastasis associated 1 protein (MTA-1). We have earlier shown that in the context of HCC and normal liver cell lines, HuH6 and THLE-2, respectively. MTA-1 protein is actively stabilized in HCC cell lines and actively degraded in normal liver cells. We had also shown that TRIM25 is the E3 ligase that interacts with and degrades MTA-1 protein in normal liver cells. However, the exact mechanism by which TRIM25 degrades MTA-1 protein has still not been elucidated. In the study, we used both in situ prediction algorithms and mass spectrometry based post-translational modification analysis to map the lysine residues in MTA-1 that are polyubiquitinated. Whereas UbPred algorithm revealed a combination of medium and low confidence sites, it revealed only one high confidence lysine (K98) residue. The hCKSAAP_UbSite algorithm also predicted K98 site. Mass spectrometry analysis also showed that K98 has ubiquitin modification. Immunofluorescence analysis showed that in normal liver cell line, THLE-2, which has high expression of TRIM25, ectopically expressed FLAG-tagged wild-type MTA-1 was actively degraded, but the K98R mutant MTA-1 was not. In vitro ubiquitination assay using recombinant wild-type and K98R mutant MTA-1 confirmed that MTA-1 is poly-ubiquitinated at K98 residue by TRIM25. The K98R mutant had a longer half-life than wild-type MTA-1 protein in an in vitro protein stability assay. We establish that TRIM25 ubiquitinates MTA-1 at lysine 98 and degrades it normal liver cells.