Three Arabidopsis UMP kinases have different roles in pyrimidine nucleotide biosynthesis and (deoxy)CMP salvage.

Pyrimidine nucleotide monophosphate biosynthesis ends in the cytosol with uridine monophosphate (UMP). UMP phosphorylation to uridine diphosphate (UDP) by UMP KINASEs (UMKs) is required for the generation of all pyrimidine (deoxy)nucleoside triphosphates as building blocks for nucleic acids and central metabolites like UDP-glucose. The Arabidopsis (Arabidopsis thaliana) genome encodes five UMKs and three belong to the AMP KINASE (AMK)-like UMKs, which were characterized to elucidate their contribution to pyrimidine metabolism. Mitochondrial UMK2 and cytosolic UMK3 are evolutionarily conserved, whereas cytosolic UMK1 is specific to the Brassicaceae. In vitro, all UMKs can phosphorylate UMP, cytidine monophosphate (CMP) and deoxycytidine monophosphate (dCMP), but with different efficiencies. Clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated nuclease 9 (Cas9)-induced null mutants were generated for UMK1 and UMK2, but not for UMK3, since frameshift alleles were lethal for germline cells. However, a mutant with diminished UMK3 activity showing reduced growth was obtained. Metabolome analyses of germinating seeds and adult plants of single- and higher-order mutants revealed that UMK3 plays an indispensable role in the biosynthesis of all pyrimidine (deoxy)nucleotides and UDP-sugars, while UMK2 is important for dCMP recycling that contributes to mitochondrial DNA stability. UMK1 is primarily involved in CMP recycling. We discuss the specific roles of these UMKs referring also to the regulation of pyrimidine nucleoside triphosphate synthesis.

Uridine-cytidine kinase 2 potentiates the mutagenic influence of the antiviral ß-d-N4-hydroxycytidine.

Molnupiravir (EIDD-2801) is an antiviral that received approval for the treatment of severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) infection. Treatment of bacteria or cell lines with the active form of molnupiravir, ß-d-N4-hydroxycytidine (NHC, or EIDD-1931), induces mutations in DNA. Yet these results contrast in vivo genotoxicity studies conducted during registration of the drug. Using a CRISPR screen, we found that inactivating the pyrimidine salvage pathway component uridine-cytidine kinase 2 (Uck2) renders cells more tolerant of NHC. Short-term exposure to NHC increased the mutation rate in a mouse myeloid cell line, with most mutations being T:A to C:G transitions. Inactivating Uck2 impaired the mutagenic activity of NHC, whereas over-expression of Uck2 enhanced mutagenesis. UCK2 is upregulated in many cancers and cell lines. Our results suggest differences in ribonucleoside metabolism contribute to the variable mutagenicity of NHC observed in cancer cell lines and primary tissues.

An optimized chemical-genetic method for cell-specific metabolic labeling of RNA.

Tissues and organs are composed of diverse cell types, which poses a major challenge for cell-type-specific profiling of gene expression. Current metabolic labeling methods rely on exogenous pyrimidine analogs that are only incorporated into RNA in cells expressing an exogenous enzyme. This approach assumes that off-target cells cannot incorporate these analogs. We disprove this assumption and identify and characterize the enzymatic pathways responsible for high background incorporation. We demonstrate that mammalian cells can incorporate uracil analogs and characterize the enzymatic pathways responsible for high background incorporation. To overcome these limitations, we developed a new small molecule-enzyme pair consisting of uridine/cytidine kinase 2 and 2'-azidouridine. We demonstrate that 2'-azidouridine is only incorporated in cells expressing uridine/cytidine kinase 2 and characterize selectivity mechanisms using molecular dynamics and X-ray crystallography. Furthermore, this pair can be used to purify and track RNA from specific cellular populations, making it ideal for high-resolution cell-specific RNA labeling. Overall, these results reveal new aspects of mammalian salvage pathways and serve as a new benchmark for designing, characterizing and evaluating methodologies for cell-specific labeling of biomolecules.

Characterization of uridine-cytidine kinase like-1 nucleoside kinase activity and its role in tumor growth.

Uridine-cytidine kinase like-1 (UCKL-1) is a largely uncharacterized protein with high sequence similarity to other uridine-cytidine kinases (UCKs). UCKs play an important role in the pyrimidine salvage pathway, catalyzing the phosphorylation of uridine and cytidine to UMP and CMP, respectively. Only two human UCKs have been identified, UCK1 and UCK2. Previous studies have shown both enzymes phosphorylate uridine and cytidine using ATP as the phosphate donor. No studies have evaluated the kinase potential of UCKL-1. We cloned and purified UCKL-1 and found that it successfully phosphorylated uridine and cytidine using ATP as the phosphate donor. The catalytic efficiency (calculated as kcat/KM) was 1.2 × 104 s-1, M-1 for uridine and 0.7 × 104 s-1, M-1 for cytidine. Our lab has previously shown that UCKL-1 is up-regulated in tumor cells, providing protection against natural killer (NK) cell killing activity. We utilized small interfering RNA (siRNA) to down-regulate UCKL-1 in vitro and in vivo to determine the effect of UCKL-1 on tumor growth and metastasis. The down-regulation of UCKL-1 in YAC-1 lymphoma cells in vitro resulted in decreased cell counts and increased apoptotic activity. Down-regulation of UCKL-1 in K562 leukemia cells in vivo led to decreased primary tumor growth and less tumor cell dissemination and metastasis. These results identify UCKL-1 as a bona fide pyrimidine kinase with the therapeutic potential to be a target for tumor growth inhibition and for diminishing or preventing metastasis.

Structure-Based Prototyping of Allosteric Inhibitors of Human Uridine/Cytidine Kinase 2 (UCK2).

Pyrimidine nucleotide biosynthesis in humans is a promising chemotherapeutic target for infectious diseases caused by RNA viruses. Because mammalian cells derive pyrimidine ribonucleotides through a combination of de novo biosynthesis and salvage, combined inhibition of dihydroorotate dehydrogenase (DHODH; the first committed step in de novo pyrimidine nucleotide biosynthesis) and uridine/cytidine kinase 2 (UCK2; the first step in salvage of exogenous nucleosides) strongly attenuates viral replication in infected cells. However, while several pharmacologically promising inhibitors of human DHODH are known, to date there are no reports of medicinally viable leads against UCK2. Here, we use structure-based drug prototyping to identify two classes of promising leads that noncompetitively inhibit UCK2 activity. In the process, we have identified a hitherto unknown allosteric site at the intersubunit interface of this homotetrameric enzyme. By reducing the kcat of human UCK2 without altering its KM, these new inhibitors have the potential to enable systematic dialing of the fractional inhibition of pyrimidine salvage to achieve the desired antiviral effect with minimal host toxicity.

Adult T-cell leukemia-lymphoma acquires resistance to DNA demethylating agents through dysregulation of enzymes involved in pyrimidine metabolism.

Adult T-cell leukemia-lymphoma (ATL) is an aggressive neoplasm derived from T-cells transformed by human T-cell lymphotropic virus-1 (HTLV-1). Recently, we reported that regional DNA hypermethylation in HTLV-1-infected T-cells reflects the disease status of ATL and the anti-ATL effects of DNA demethylating agents, including azacitidine (AZA), decitabine (DAC) and a new DAC prodrug, OR-2100 (OR21), which we developed. Here, to better understand the mechanisms underlying drug resistance, we generated AZA-, DAC- and OR21-resistant (AZA-R, DAC-R and OR21-R, respectively) cells from the ATL cell line TL-Om1 and the HTLV-1-infected cell line MT-2 via long-term drug exposure. The efficacy of OR21 was almost the same as that of DAC, indicating that the pharmacodynamics of OR21 were due to release of DAC from OR21. Resistant cells did not show cellular responses observed in parental cells induced by treatment with drugs, including growth suppression, depletion of DNA methyltransferase DNMT1 and DNA hypomethylation. We also found that reduced expression of deoxycytidine kinase (DCK) correlated with lower susceptibility to DAC/OR21 and that reduced expression of uridine cytidine kinase2 (UCK2) correlated with reduced susceptibility to AZA. DCK and UCK2 catalyze phosphorylation of DAC and AZA, respectively; reconstitution of expression reversed the resistant phenotypes. A large homozygous deletion in DCK and a homozygous splice donor site mutation in UCK2 were identified in DAC-R TL-Om1 and AZA-R TL-Om1, respectively. Both genomic mutations might lead to loss of protein expression. Thus, inactivation of UCK2 and DCK might be a putative cause of phenotypes that are resistant to AZA and DAC/OR21, respectively.

UCK2 regulated by miR-139-3p regulates the progression of hepatocellular carcinoma cells.

Objective: This study mainly explores how UCK2 impacts the progression of hepatocellular carcinoma (HCC). Methods: Mature miRNA and mRNA expression data along with the clinical data of HCC were provided by The Cancer Genome Atlas to mine differentially expressed miRNAs and mRNAs. Expression levels of UCK2 and miR-139-3p in HCC were tested through quantitative real-time PCR. How UCK2 and miR-139-3p impacted HCC cell activities were detected by Transwell, wound healing and cell proliferation approaches. Whether miR-139-3p could bind to UCK2 was detected by dual-luciferase assay. Results: This investigation found evidently high levels of UCK2 in both HCC tissue and cells and its marked association with poor prognosis. Overexpression of UCK2 could significantly promote the behaviors of HCC cells. In addition, poorly expressed miR-139-3p was inversely associated with UCK2. Dual-luciferase method also proved the association. The rescue experiment showed that miR-139-3p regulated cell behaviors in HCC through targeting UCK2. Conclusion: Highly expressed UCK2 was mediated by miR-139-3p to modulate cell behaviors in HCC. It is assumed that UCK2 is a possible target of HCC for cancer therapy purposes.

Globally, a large number of patients succumb to hepatocellular carcinoma (HCC) each year. Only 10­37% patients can undergo surgery because of hepatic failure and advanced tumors. Though the recovery rate after excision is 20­30%, the 5-year survival rate is low, and postoperative recurrence rate is high. Despite the widespread application of HCC screening, only few patients in the early stage have been diagnosed. Hence, it is urgent to explore its potential mechanism. This study investigates the relationship between aberrant expression of mRNA and malignancy of HCC cells. Finally, the abnormally high expression of UCK2 is correlated with patients' low survival rate and poor prognosis.

Targeting uridine-cytidine kinase 2 induced cell cycle arrest through dual mechanism and could improve the immune response of hepatocellular carcinoma.

BACKGROUND: Pyrimidine metabolism is critical for tumour progression. Uridine-cytidine kinase 2 (UCK2), a key regulator of pyrimidine metabolism, is elevated during hepatocellular carcinoma (HCC) development and exhibits carcinogenic effects. However, the key mechanism of UCK2 promoting HCC and the therapeutic value of UCK2 are still undefined. The aim of this study is to investigate the potential of UCK2 as a therapeutic target for HCC. METHODS: Gene expression matrices were obtained from public databases. RNA-seq, co-immunoprecipitation and RNA-binding protein immunoprecipitation were used to determine the mechanism of UCK2 promoting HCC. Immune cell infiltration level and immune-related functional scores were evaluated to assess the link between tumour microenvironment and UCK2. RESULTS: In HCC, the expression of UCK2 was upregulated in part by TGFß1 stimulation. UCK2 promoted cell cycle progression of HCC by preventing the degradation of mTOR protein and maintaining the stability of PDPK1 mRNA. We also identified UCK2 as a novel RNA-binding protein. Downregulation of UCK2 induced cell cycle arrest and activated the TNFα/NFκB signalling pathway-related senescence-associated secretory phenotype to modify the tumour microenvironment. Additionally, UCK2 was a biomarker of the immunosuppressive microenvironment. Downregulated UCK2 induced a secretory phenotype, which could improve the microenvironment, and decreased UCK2 remodelling metabolism could lower the resistance of tumour cells to T-cell-mediated killing. CONCLUSIONS: Targeting UCK2 inhibits HCC progression and could improve the response to immunotherapy in patients with HCC. Our study suggests that UCK2 could be an ideal target for HCC.

Genomic Binding Patterns of Forkhead Box Protein O1 Reveal Its Unique Role in Cardiac Hypertrophy.

BACKGROUND: Cardiac hypertrophic growth is mediated by robust changes in gene expression and changes that underlie the increase in cardiomyocyte size. The former is regulated by RNA polymerase II (pol II) de novo recruitment or loss; the latter involves incremental increases in the transcriptional elongation activity of pol II that is preassembled at the transcription start site. The differential regulation of these distinct processes by transcription factors remains unknown. Forkhead box protein O1 (FoxO1) is an insulin-sensitive transcription factor that is also regulated by hypertrophic stimuli in the heart. However, the scope of its gene regulation remains unexplored. METHODS: To address this, we performed FoxO1 chromatin immunoprecipitation-deep sequencing in mouse hearts after 7 days of isoproterenol injections (3 mg·kg-1·mg-1), transverse aortic constriction, or vehicle injection/sham surgery. RESULTS: Our data demonstrate increases in FoxO1 chromatin binding during cardiac hypertrophic growth, which positively correlate with extent of hypertrophy. To assess the role of FoxO1 on pol II dynamics and gene expression, the FoxO1 chromatin immunoprecipitation-deep sequencing results were aligned with those of pol II chromatin immunoprecipitation-deep sequencing across the chromosomal coordinates of sham- or transverse aortic constriction-operated mouse hearts. This uncovered that FoxO1 binds to the promoters of 60% of cardiac-expressed genes at baseline and 91% after transverse aortic constriction. FoxO1 binding is increased in genes regulated by pol II de novo recruitment, loss, or pause-release. In vitro, endothelin-1- and, in vivo, pressure overload-induced cardiomyocyte hypertrophic growth is prevented with FoxO1 knockdown or deletion, which was accompanied by reductions in inducible genes, including Comtd1 in vitro and Fstl1 and Uck2 in vivo. CONCLUSIONS: Together, our data suggest that FoxO1 may mediate cardiac hypertrophic growth via regulation of pol II de novo recruitment and pause-release; the latter represents the majority (59%) of FoxO1-bound, pol II-regulated genes after pressure overload. These findings demonstrate the breadth of transcriptional regulation by FoxO1 during cardiac hypertrophy, information that is essential for its therapeutic targeting.

Identification of a four-gene metabolic signature predicting overall survival for hepatocellular carcinoma.

While hundreds of consistently altered metabolic genes had been identified in hepatocellular carcinoma (HCC), the prognostic role of them remains to be further elucidated. Messenger RNA expression profiles and clinicopathological data were downloaded from The Cancer Genome Atlas-Liver Hepatocellular Carcinoma and GSE14520 data set from the Gene Expression Omnibus database. Univariate Cox regression analysis and lasso Cox regression model established a novel four-gene metabolic signature (including acetyl-CoA acetyltransferase 1, glutamic-oxaloacetic transaminase 2, phosphatidylserine synthase 2, and uridine-cytidine kinase 2) for HCC prognosis prediction. Patients in the high-risk group shown significantly poorer survival than patients in the low-risk group. The signature was significantly correlated with other negative prognostic factors such as higher α-fetoprotein. The signature was found to be an independent prognostic factor for HCC survival. Nomogram including the signature shown some clinical net benefit for overall survival prediction. Furthermore, gene set enrichment analyses revealed several significantly enriched pathways, which might help explain the underlying mechanisms. Our study identified a novel robust four-gene metabolic signature for HCC prognosis prediction. The signature might reflect the dysregulated metabolic microenvironment and provided potential biomarkers for metabolic therapy and treatment response prediction in HCC.

Uridine-cytidine kinase 2 (UCK2): A potential diagnostic and prognostic biomarker for lung cancer.

Lung cancer has the highest morbidity and mortality among all cancers. Discovery of early diagnostic and prognostic biomarkers of lung cancer can greatly facilitate the survival rate and reduce its mortality. In our study, by analyzing Gene Expression Omnibus and Oncomine databases, we found a novel potential oncogene uridine-cytidine kinase 2 (UCK2), which was overexpressed in lung tumor tissues compared to adjacent nontumor tissues or normal lung. Then we confirmed this finding in clinical samples. Specifically, UCK2 was identified as highly expressed in stage IA lung cancer with a high diagnostic accuracy (area under the receiver operating characteristic curve > 0.9). We also found that high UCK2 expression was related to poorer clinicopathological features, such as higher T stage and N stage and higher probability of early recurrence. Furthermore, we found that patients with high UCK2 expression had poorer first progression survival and overall survival than patients with low UCK2 expression. Univariate and multivariate Cox regression analyses showed that UCK2 was an independent risk factor related with worse DFS and OS. By gene set enrichment analysis, tumor-associated biological processes and signaling pathways were enriched in the UCK2 overexpression group, which indicated that UCK2 might play a vital role in lung cancer. Furthermore, in cytology experiments, we found that knockdown of UCK2 could suppress the proliferation and migration of lung cancer cells. In conclusion, our study indicated that UCK2 might be a potential early diagnostic and prognostic biomarker for lung cancer.

Uridine-cytidine kinase 2 upregulation predicts poor prognosis of hepatocellular carcinoma and is associated with cancer aggressiveness.

Patients with advanced hepatocellular carcinoma (HCC) continue to have a dismal prognosis. Potential biomarkers to determine prognosis and select targeted therapies are urgently needed for patients with HCC. This study aimed to elucidate the role of UCK2 in HCC prognosis and tumor progression. We performed a screen of public databases to identify functional genes associated with HCC tumorigenesis, progression, and outcome. We identified uridine-cytidine kinase 2 (UCK2) as a gene of interest for further study. UCK2 promoting HCC aggressiveness was demonstrated by evaluation of clinical samples, in vitro experiments, in vivo tumorigenicity, and transcript analysis. UCK2 expression was generally elevated in HCC and was significantly correlated with poor survival and inferior clinicopathological characteristics of HCC patients. A multivariate analysis revealed that high UCK2 expression was an independent factor for poor prognosis. In HCC cell lines, UCK2 knockdown suppressed cell migration and invasion and inhibited cell proliferation, while UCK2 overexpression had an opposite effect. Animal model experiments confirmed that knockdown of UCK2 suppressed tumor growth in vivo. The bioinformatics analysis demonstrated that UCK2 might associated with metabolsim, splicesome, and adherens junction. UCK2 is highly associated with HCC malignant behavior and is a potential prognostic predictor for HCC patients in the clinic.

UCK2 upregulation might serve as an indicator of unfavorable prognosis of hepatocellular carcinoma.

Uridine-cytidine kinases (encoded by UCK1, UCKL1, and UCK2) catalyze the phosphorylation of uridine and cytidine to uridine monophosphate (UMP) and cytidine monophosphate (CMP). In this study, using data from the Cancer Genome Atlas (TCGA), we analyzed the expression profile of uridine-cytidine kinase genes in hepatocellular carcinoma (HCC), their prognostic value, and the epigenetic alterations associated with their dysregulation. Results showed that UCKL1 and UCK2, but not UCK1 were significantly upregulated in HCC tissues than in adjacent normal tissues. Only UCK2 was significantly upregulated in the deceased group and the recurrence group, compared to the control groups. Multivariate analysis confirmed that increased UCK2 expression was an independent prognostic indicator of shorter overall survival (OS) (HR: 1.760, 95% CI: 1.398-2.216, P < 0.001) and recurrence-free survival (RFS) (HR: 1.543, 95% CI: 1.232-1.933, P < 0.001). Two CpG sites (cg09277749 and cg21143899) were significantly hypomethylated in HCC tissues than in adjacent normal tissues and were negatively correlated with UCK2 expression. However, survival analysis showed that only high methylation of cg0927774 was associated with better OS and RFS of HCC patients. Based on the findings above, we infer that UCK2 upregulation might be a valuable prognostic marker in HCC. The methylation of status cg0927774 might play a critical role in its expression. © 2018 IUBMB Life, 71(1):105-112, 2019.

Discovery of small molecule inhibitors of human uridine-cytidine kinase 2 by high-throughput screening.

Clinically relevant inhibitors of dihydroorotate dehydrogenase (DHODH), a rate-limiting enzyme in mammalian de novo pyrimidine synthesis, have strong antiviral and anticancer activity in vitro. However, they are ineffective in vivo due to efficient uridine salvage by infected or rapidly dividing cells. The pyrimidine salvage enzyme uridine-cytidine kinase 2 (UCK2), a ∼29 kDa protein that forms a tetramer in its active state, is necessary for uridine salvage. Notwithstanding the pharmacological potential of this target, no medicinally tractable inhibitors of the human enzyme have been reported to date. We therefore established and miniaturized an in vitro assay for UCK2 activity and undertook a high-throughput screen against a ∼40,000-compound library to generate drug-like leads. The structures, activities, and modes of inhibition of the most promising hits are described. Notably, our screen yielded non-competitive UCK2 inhibitors which were able to suppress nucleoside salvage in cells both in the presence and absence of DHODH inhibitors.

Impact of the Uridine⁻Cytidine Kinase Like-1 Protein and IL28B rs12979860 and rs8099917 SNPs on the Development of Hepatocellular Carcinoma in Cirrhotic Chronic Hepatitis C Patients-A Pilot Study.

Background and objectives: The hepatitis C virus (HCV) is the major causative agent of hepatocellular carcinoma (HCC) in the western world. The efficacy of surveillance programs for early detection of HCC is not satisfactory: many tumors are diagnosed at the late, incurable stages. Therefore, there is a need in reliable prognostic markers for the proper follow-up of HCV-positive patients. The aim of the present study was to assess the prognostic value of the uridine⁻cytidine kinase-like protein 1 (UCKL-1), a putative oncoprotein, together with genetically determined polymorphisms in the interleukin 28B (IL28B) gene (rs12979860, rs8099917) in the development of HCC in HCV-positive cirrhotic patients. Materials and Methods: We included 32 HCV cirrhotic patients, 21 (65.6%) of whom had HCC. The expression of UCKL-1 was assessed in liver tissue sections, using immunohistochemistry. For IL28B rs12979860 and rs8099917 genotype analysis, the corresponding genomic regions were amplified by polymerase chain reaction (PCR) with appropriate primers. Results: We have found that UCKL-1 expression was significantly increased in HCC (p = 0.003). The presence of rs8099917 TT single-nucleotide polymorphism (SNP) elevated the chances of HCC manifestation more than sevenfold (OR = 7.3, p = 0.0273). The presence of rs12979860 CC SNP also heightened HCC chances more than sevenfold (OR = 7.5, p = 0.0765). Moreover, in the HCC group, a combination of IL28B rs12979860 non-TT and rs8099917 TT genotypes was observed more often, compared with the non-HCC group. Other combinations of IL28B rs12979860 and rs8099917 SNIPs were associated with a reduced risk of HCC development, approximately at the same extent. Conclusions: The presence of IL28B rs8099917 TT and rs12979860 CC SNPs, but not the intensity of UCKL-1 expression, is strongly associated with increased chances of HCC development in HCV-positive cirrhotic patients.

The pivotal role of uridine-cytidine kinases in pyrimidine metabolism and activation of cytotoxic nucleoside analogues in neuroblastoma.

Uridine-cytidine kinase (UCK) catalyzes the phosphorylation of uridine and cytidine as well as the pharmacological activation of several cytotoxic pyrimidine ribonucleoside analogues. In this study, we investigated the functional role of two isoforms of UCK in neuroblastoma cell lines. Analysis of mRNA coding for UCK1 and UCK2 showed that UCK2 is the most abundantly expressed UCK in a panel of neuroblastoma cell lines. Transient and stable overexpression of UCK2 in neuroblastoma cells increased the metabolism of uridine and cytidine as well as the cytotoxicity of 3-deazauridine. Knockdown of endogenous UCK2 as well as overexpression of UCK1 resulted in decreased metabolism of uridine and cytidine and protected the neuroblastoma cells from 3-deazauridine-induced toxicity. Subcellular localization studies showed that UCK1-GFP and UCK2-GFP were localized in the cell nucleus and cytosol, respectively. However, co-expression of UCK1 with UCK2 resulted in a nuclear localization of UCK2 instead of its normal cytosolic localization, thereby impairing its normal function. The physical association of UCK1 and UCK2 was further demonstrated through pull-down analysis using his-tagged UCK. The discovery that UCK2 is highly expressed in neuroblastoma opens the possibility for selectively targeting neuroblastoma cells using UCK2-dependent pyrimidine analogues, while sparing normal tissues.

A pentose bisphosphate pathway for nucleoside degradation in Archaea.

Owing to the absence of the pentose phosphate pathway, the degradation pathway for the ribose moieties of nucleosides is unknown in Archaea. Here, in the archaeon Thermococcus kodakarensis, we identified a metabolic network that links the pentose moieties of nucleosides or nucleotides to central carbon metabolism. The network consists of three nucleoside phosphorylases, an ADP-dependent ribose-1-phosphate kinase and two enzymes of a previously identified NMP degradation pathway, ribose-1,5-bisphosphate isomerase and type III ribulose-1,5-bisphosphate carboxylase/oxygenase. Ribose 1,5-bisphosphate and ribulose 1,5-bisphosphate are intermediates of this pathway, which is thus designated the pentose bisphosphate pathway.

Role of the uridine/cytidine kinase 2 mutation in cellular sensitiveness toward 3'-ethynylcytidine treatment of human cancer cells.

A nucleosidic medicine, 1-(3-C-ethynyl-ß-D-ribo-pentofuranosyl)cytosine [3'-ethynylcytidine (ECyd)], is a potent inhibitor of RNA polymerase I and shows anticancer activity to various human solid tumors in vitro and in vivo. ECyd is phosphorylated to 3'-ethyntlcytidine 5'-monophosphate by uridine/cytidine kinase 2 (UCK2) and subsequently further to diphosphate and triphosphate (3'-ethyntlcytidine 5'-diphosphate, 3'-ethyntlcytidine 5'-triphosphate). 3'-Ethyntlcytidine 5'-triphosphate is an active metabolite that can inhibit RNA polymerase I competitively, causing cancer cell death. Here, to identify the UCK2 mutation for detecting responder or nonresponder to ECyd, we investigated the relationship between point mutation of the UCK2 gene and response to ECyd in various human solid tumors. We identified several functional point mutations including the splice-site mutation of the UCK2 gene IVS5+5 G>A. In addition, we found that the IVS5+5 G>A variant generates an aberrant mRNA transcript, namely, truncated mRNA was produced and normal mRNA levels were markedly decreased in the ECyd-resistant cancer cell line HT1080. We concluded that these findings strongly suggest that the IVS5+5 G>A variant would affect the expression level of the UCK2 transcript, resulting in decreased sensitivity to ECyd.

In Silico Discovery of Potential Uridine-Cytidine Kinase 2 Inhibitors from the Rhizome of Alpinia mutica.

Uridine-cytidine kinase 2 is implicated in uncontrolled proliferation of abnormal cells and it is a hallmark of cancer, therefore, there is need for effective inhibitors of this key enzyme. In this study, we employed the used of in silico studies to find effective UCK2 inhibitors of natural origin using bioinformatics tools. An in vitro kinase assay was established by measuring the amount of ADP production in the presence of ATP and 5-fluorouridine as a substrate. Molecular docking studies revealed an interesting ligand interaction with the UCK2 protein for both flavokawain B and alpinetin. Both compounds were found to reduce ADP production, possibly by inhibiting UCK2 activity in vitro. In conclusion, we have identified flavokawain B and alpinetin as potential natural UCK2 inhibitors as determined by their interactions with UCK2 protein using in silico molecular docking studies. This can provide information to identify lead candidates for further drug design and development.

Testicular germ cell tumor susceptibility associated with the UCK2 locus on chromosome 1q23.

Genome-wide association studies (GWASs) have identified multiple common genetic variants associated with an increased risk of testicular germ cell tumors (TGCTs). A previous GWAS reported a possible TGCT susceptibility locus on chromosome 1q23 in the UCK2 gene, but failed to reach genome-wide significance following replication. We interrogated this region by conducting a meta-analysis of two independent GWASs including a total of 940 TGCT cases and 1559 controls for 122 single-nucleotide polymorphisms (SNPs) on chromosome 1q23 and followed up the most significant SNPs in an additional 2202 TGCT cases and 2386 controls from four case-control studies. We observed genome-wide significant associations for several UCK2 markers, the most significant of which was for rs3790665 (PCombined = 6.0 × 10(-9)). Additional support is provided from an independent familial study of TGCT where a significant over-transmission for rs3790665 with TGCT risk was observed (PFBAT = 2.3 × 10(-3)). Here, we provide substantial evidence for the association between UCK2 genetic variation and TGCT risk.