Deoxyribonucleotides (dNTPs) are important for the efficient growth of DNA viruses. Therefore, many DNA viruses have strategies for the upregulation of cellular dNTP levels. Both α- and γ-herpesviruses encode functional homologs of cellular dNTP anabolic enzymes, including the class I ribonucleotide reductase (RNR) large (R1) and small (R2) subunits, whereas β-herpesviruses modulate host cells to induce genes that increase dNTP levels. Interestingly, β-herpesviruses still express the nonfunctional RNR R1 subunit. However, it is not clear why β-herpesviruses still carry inactive R1 homologs. Recently, the R1 homologs of herpesviruses have been shown to inhibit innate immune signaling pathways. In particular, both functional and nonfunctional R1 homologs target receptor-interacting protein kinase 1 (RIP1) and inhibit RIP1-mediated signaling pathways to promote viral replication. Here, we summarize recent findings on the activity of herpesviral R1 homologs and discuss their roles in the regulation of innate immune signaling pathways.
Deoxyribonucleotides ; DNA Viruses ; Herpesviridae ; Protein Kinases ; Ribonucleotide Reductases* ; Up-Regulation

BACKGROUND: LOH11A is a region with frequent allele loss (>75%) in lung cancer that is located on the centromeric part of chromosome 11p15.5. Clinical and cell biological studies suggest that this region contains a gene associated with metastatic tumor spread. RRM1 encoding the M1 subunit of ribonucleotide reductase, which is an enzyme that catalyses the rate-limiting step in deoxyribonucleotide synthesis, is located in the LOH11A region. METHODS: Polymorphisms were found at nucleotide position (-)37 (C/A) and (-)524 (C/T) from the beginning of exon 1 of the RRM1 gene that might regulate the expression of RRM1. We studied the polymorphisms in 127 Korean individuals (66 lung cancer and 61 normal controls) and compared with those of 140 American patients with lung cancer. RESULTS: CC, AC and AA were found at the (-)37 position in 64(50.4%), 55(43.3%), and 8(6.3%) out of 127 Korean individuals (66 cancer, 61 non-cancer patients), respectively. There was a similar frequency of allele A at (-)37 in the American(27.9%) and Korean population(28.0%). CC, CT and TT was found at the (-)524 position in 24(18.9%), 44(34.6%), and 59(46.5%) out of the 127 Korean individuals, respectively. There was a similar frequency of allele C at (-)524 in the American(34.6%) and Korean population(36.2%).There was no difference in the frequency of the (-)37 and (-)524 genotypes between the cancer and non-cancer group. However there was a significant correlation of the genotypes between (-)37 and (-)524 (p<0.001), which suggests the possible coordination of these polymorphisms in the regulation of the promoter activity of the RRM1 gene. CONCLUSION: RRM1 promoter polymorphisms were not found to be significant risk factors for lung cancer. However, a further study of the promoter activity and expression of the RRM1 gene according to the pattern of the polymorphism will be needed.
Alleles ; Catalysis ; Exons ; Genes, vif ; Genotype ; Humans ; Lung Neoplasms* ; Lung* ; Ribonucleotide Reductases ; Risk Factors

The Ribonucleotide reductases (RNR) are essential enzymes that catalyze the conversion of nucleotides to deoxynucleotides in DNA replication and repair in all living organisms. The RNRs operate by a free radical mechanism but differ in the composition of subunit, cofactor required and regulation by allostery. Based on these differences the RNRs are classified into three classes-class I, class II and class III which depend on oxygen, adenosylcobalamin and S-adenosylmethionine with an iron sulfur cluster respectively for radical generation. In this article thirty seven sequences belonging to each of the three classes of RNR were analyzed by using various tools of bioinformatics. Phylogenetic analysis, dot-plot comparisons and motif analysis was done to identify a number of differences in the three classes of RNRs. In this research article, we have attempted to decipher evolutionary relationship between the three classes of RNR by using bioinformatics approach.
Cobamides ; Computational Biology ; DNA Replication ; Iron ; Nucleotides ; Oxygen ; Ribonucleotide Reductases ; S-Adenosylmethionine ; Sulfur

Unstable hemoglobins (Hb) are variants of adult Hb that tend to precipitate and form insoluble inclusions (Heinz bodies) within red blood cells (RBC) and RBC precursors. More than 100 structurally different unstable Hb variants showing broad spectrum of manifestations from asymptomatic to severe hemolytic anemia and dyserythropoiesis have been discovered. Hydroxyurea is a potent ribonucleotide reductase inhibitor and have been proposed as a new therapy for beta chain hemoglobinopathies through activation of gamma chain synthesis. We treated two patients (A : son, B : father) with highly unstable Hb diagnosed as Hb Madrid [Beta 115(G17)Ala->Pro] by direct DNA sequencing and restriction enzyme analysis. Our patients received hydroxyurea in dosages varying from 0.75g to 1.3g daily for 89 weeks. We could not show the clinical and hematological improvements after hydroxyurea therapy in thses patients. Optimization of dosage and long term side effects of hydroxyurea should be studied further.
Adult ; Anemia, Hemolytic ; Erythrocytes ; Hemoglobinopathies ; Humans ; Hydroxyurea* ; Restriction Mapping ; Ribonucleotide Reductases ; Sequence Analysis, DNA

OBJECTIVE: Meningiomas represent 18-20% of all intracranial tumors and have a 20-50% 10-year recurrence rate, despite aggressive surgery and irradiation. Hydroxyurea, an inhibitor of ribonucleotide reductase, is known to inhibit meningioma cells by induction of apoptosis. We report the long-term follow-up result of hydroxyurea therapy in the patients with recurrent meningiomas. METHODS: Thirteen patients with recurrent WHO grade I or II meningioma were treated with hydroxyurea (1000 mg/m2/day orally divided twice per day) from June 1998 to February 2012. Nine female and 4 male, ranging in age from 32 to 83 years (median age 61.7 years), were included. Follow-up assessment included physical examination, computed tomography, and magnetic resonance imaging (MRI). Standard neuro-oncological response criteria (Macdonald criteria) were used to evaluate the follow-up MRI scans. The treatment was continued until there was objective disease progression or onset of unmanageable toxicity. RESULTS: Ten of the 13 patients (76.9%) showed stable disease after treatment, with time to progression ranging from 8 to 128 months (median 72.4 months; 6 patients still accruing time). However, there was no complete response or partial response in any patients. Three patients had progressive disease after 88, 89, 36 months, respectively. There was no severe (Grade III-IV) blood systemic disorders and no episodes of non-hematological side effects. CONCLUSION: This study showed that hydroxyurea is a modestly active agent against recurrent meningiomas and can induce long-term stabilization of disease in some patients. We think that hydroxyurea treatment is well tolerated and convenient, and could be considered as an alternative treatment option in patients with recurrent meningiomas prior to reoperation or radiotherapy.
Apoptosis ; Disease Progression ; Female ; Follow-Up Studies ; Humans ; Hydroxyurea ; Magnetic Resonance Imaging ; Male ; Meningioma ; Physical Examination ; Recurrence ; Reoperation ; Ribonucleotide Reductases

OBJECTIVETo study the expression of the small subunit ribonucleotide reductase (R2) in gestational trophoblastic diseases (GTD) and to assess its prognostic value.

METHODSThe expression of R2 was detected with immunohistochemical method in 15 cases of normal villi, 38 cases of hydatidiform mole (HM), 42 cases of invasive moles (IM) and 18 cases of choriocarcinoma (CC).

RESULTSR2 expression in HM, IM and CC was significantly increased compared with that of normal villi (P=0.000). There were no significant differences in R2 protein expression among HM, IM and CC. Among 38 cases of HM, R2 expression in 8 cases with malignant transformation was significantly higher than in 30 cases of non-malignant transformation mole (P=0.02). Preoperative chemotherapy of gestational trophoblastic tumor including IM and CC did not influence the R2 expression. Compared with patients of stage I (WHO), the R2 protein in gestational trophoblastic tumor (GTT) patients of stage III or stage II was significantly increased (P=0.023 and P=0.038, respectively). The value of R2 in GTT patients with middle or high risk in WHO prognostic scoring system was higher than in the patients with low risk (P=0.018 and P=0.006, respectively).

CONCLUSIONR2 expression in GTD is increased, which may be associated with the hyperplasia of trophoblasts, malignant transformation of hydatidiform mole and drug resistance of trophoblastic tumor.

Adult ; Female ; Gestational Trophoblastic Disease ; enzymology ; pathology ; Humans ; Pregnancy ; Ribonucleotide Reductases ; biosynthesis ; genetics ; Uterine Neoplasms ; enzymology ; pathology

OBJECTIVE: To analyze the clinical characteristics and pathogenic gene in a Chinese pedigree affected with mitochondrial DNA depletion syndrome 8A (MTDPS8A). METHODS: Whole exome sequencing was carried out for the patient. Sanger sequencing was used to verify the results, and PolyPhen-2 and PROVEAN software were used to predict the impact of amino acid changes on the function of the protein. RESULTS: The patient, a two-month-old female, was admitted to the hospital for poor milk intake and poor mental response. Her clinical manifestations included feeding difficulty, shortness of breath and low muscle tone. Auxiliary laboratory test indicated that the infant was underdeveloped with abnormal liver, kidney, and heart functions accompanied by hyperlacticacidemia. She responded poorly to treatment and eventually died. Sequencing revealed that the child has carried compound heterozygous missense variants of the RRM2B gene, namely c.16delA (p.R6Gfs*22) and c.175G>C (p.A59P), which were respectively inherited from her father and mother, and both were newly discovered pathologic variants. CONCLUSION The c.16delA and c.175G>C compound heterozygous variants of the RRM2B gene probably underlay the pathogenesis of MTDPS8A. Above finding has strengthened the understanding of the clinical feature and genetic etiology of this disease and expanded the mutation spectrum of the RRM2B gene.
Cell Cycle Proteins ; Child ; China ; DNA, Mitochondrial/genetics* ; Female ; Genetic Testing ; Humans ; Infant ; Mutation ; Pedigree ; Ribonucleotide Reductases ; Whole Exome Sequencing

Hydroxyurea, one of conventional chemotherapies in chronic myelogenous leukemia(CML) and polycythemia vera, inhibits ribonucleotide reductase, which catalyzes the rate-limiting step in the de novo synthesis of deoxynucleotide triphosphates required for DNA synthesis. Various cutaneous side effects due to hydroxyurea have been reported as follows; alopecia, diffuse hyperpigmentation, scaling, poikiloderma, atrophy of the skin and subcutaneous tissues, nail changes with multiple pigmented nail bands or brittleness, erythema and scaling of acral sites simulating chronic dermatomyositis, lichen planus-like lesions, or skin tumors on the UV-light exposed areas.A 72-year-old woman, receiving hydroxyurea for CML during 5 years, revealed hydroxyurea dermopathy such as scaly papules, poikilodermatous patches, and acral ulceration, and unusually developed squamous cell carcinoma. This is a rare case of hydroxyurea dermopathy and the first case of squamous cell carcinoma by hydroxyurea in Korea.
Aged ; Alopecia ; Atrophy ; Carcinoma, Squamous Cell* ; Dermatomyositis ; DNA ; Drug Therapy ; Erythema ; Female ; Humans ; Hydroxyurea ; Hyperpigmentation ; Korea ; Lichens ; Polycythemia Vera ; Ribonucleotide Reductases ; Skin ; Subcutaneous Tissue ; Ulcer*

Eukaryotic cells contain numerous iron-requiring proteins such as iron-sulfur (Fe-S) cluster proteins, hemoproteins and ribonucleotide reductases (RNRs). These proteins utilize iron as a cofactor and perform key roles in DNA replication, DNA repair, metabolic catalysis, iron regulation and cell cycle progression. Disruption of iron homeostasis always impairs the functions of these iron-requiring proteins and is genetically associated with diseases characterized by DNA repair defects in mammals. Organisms have evolved multi-layered mechanisms to regulate iron balance to ensure genome stability and cell development. This review briefly provides current perspectives on iron homeostasis in yeast and mammals, and mainly summarizes the most recent understandings on iron-requiring protein functions involved in DNA stability maintenance and cell cycle control.
Animals ; Cell Cycle Checkpoints ; DNA ; metabolism ; DNA Repair ; DNA Replication ; Hemeproteins ; genetics ; metabolism ; Iron ; chemistry ; metabolism ; Iron-Sulfur Proteins ; genetics ; metabolism ; Ribonucleotide Reductases ; genetics ; metabolism ; Yeasts ; metabolism

OBJECTIVE: To investigate the effects of ribonucleotide reductase catalytic subunit M1 (RRM1) gene silencing on drug resistance of human breast cancer cell line MCF-7/R. METHODS: We established a paclitaxel-resistant breast cancer MCF-7 cell line (MCF-7/R) by exposing the cells to high-concentration paclitaxel in a short time. Small interfering RNAs (siRNAs) targeting RRM1 were designed to silence RRM1 expression in human breast cancer MCF-7/R cells. MTT assay was used to detect the IC values and the sensitivity to paclitaxel in the cells with or without siRNA transfection. The changes in the proliferative activity of MCF7 and MCF-7/R cells following RRM1 gene silencing were evaluated using EdU assay. Flow cytometry was used to analyze the cell apoptosis and cell cycle changes. We assessed the effect of RRM1 gene silencing and paclitaxel on the tumor growth in a nude mouse model bearing subcutaneous xenografts with or without siRNA transfection. RESULTS: We detected significantly higher expressions of RRM1 at both the mRNA and protein levels in the drug-resistant MCF- 7/R cells than in the parental MCF-7 cells ( < 0.01). Transfection with the specific siRNAs significantly reduced the expression of RRM1 in MCF-7/R cells ( < 0.05), which showed a significantly lower IC value of paclitaxel than the cells transfected with the negative control siRNA ( < 0.05). RRM1 silencing significantly inhibited the proliferation ( < 0.01) and enhanced the apoptosis-inducing effect of paclitaxel in MCF-7/R cells ( < 0.001); RRM1 silencing also resulted in obviously reduced Akt phosphorylation, suppressed Bcl-2 expression and promoted the expression of p53 protein in MCF-7/R cells. In the tumor-bearing nude mice, the volume of subcutaneously transplanted tumors was significantly smaller in MCF-7/R/siRNA+ PTX group than in the other groups ( < 0.001). CONCLUSIONS RRM1 gene silencing can reverse paclitaxel resistance in human breast cancer cell line MCF-7/R by promoting cell apoptosis.
Animals ; Apoptosis ; Breast Neoplasms ; Drug Resistance, Neoplasm ; Gene Silencing ; Humans ; MCF-7 Cells ; Mice ; Mice, Nude ; Paclitaxel ; RNA, Small Interfering ; Ribonucleotide Reductases ; Tumor Suppressor Proteins