Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 20 de 140
Filter
4.
Oncogenesis ; 3: e121, 2014 Oct 13.
Article in English | MEDLINE | ID: mdl-25310643

ABSTRACT

p53-regulated caspase-independent cell death has been implicated in suppression of tumorigenesis, however, the regulating mechanisms are poorly understood. We previously reported that 8-oxoguanine (8-oxoG) accumulation in nuclear DNA (nDNA) and mitochondrial DNA triggers two distinct caspase-independent cell death through buildup of single-strand DNA breaks by MutY homolog (MUTYH), an adenine DNA glycosylase. One pathway depends on poly-ADP-ribose polymerase (PARP) and the other depends on calpains. Deficiency of MUTYH causes MUTYH-associated familial adenomatous polyposis. MUTYH thereby suppresses tumorigenesis not only by avoiding mutagenesis, but also by inducing cell death. Here, we identified the functional p53-binding site in the human MUTYH gene and demonstrated that MUTYH is transcriptionally regulated by p53, especially in the p53/DNA mismatch repair enzyme, MLH1-proficient colorectal cancer-derived HCT116+Chr3 cells. MUTYH-small interfering RNA, an inhibitor for p53 or PARP suppressed cell death without an additive effect, thus revealing that MUTYH is a potential mediator of p53 tumor suppression, which is known to be upregulated by MLH1. Moreover, we found that the p53-proficient, mismatch repair protein, MLH1-proficient colorectal cancer cell line express substantial levels of MUTYH in nuclei but not in mitochondria, suggesting that 8-oxoG accumulation in nDNA triggers MLH1/PARP-dependent cell death. These results provide new insights on the molecular mechanism of tumorigenesis and potential new strategies for cancer therapies.

5.
Cell Death Differ ; 16(10): 1315-22, 2009 Oct.
Article in English | MEDLINE | ID: mdl-19498443

ABSTRACT

Inosine triphosphate pyrophosphatase (ITPase), the enzyme that hydrolyzes ITP and other deaminated purine nucleoside triphosphates to the corresponding purine nucleoside monophosphate and pyrophosphate, is encoded by the Itpa gene. In this study, we established Itpa knockout (KO) mice and used them to show that ITPase is required for the normal organization of sarcomeres in the heart. Itpa(-/-) mice died about 2 weeks after birth with features of growth retardation and cardiac myofiber disarray, similar to the phenotype of the cardiac alpha-actin KO mouse. Inosine nucleotides were found to accumulate in both the nucleotide pool and RNA of Itpa(-/-) mice. These data suggest that the role of ITPase in mice is to exclude ITP from the ATP pool, and the main target substrate of this enzyme is rITP. Our data also suggest that cardiomyopathy, which is mainly caused by mutations in sarcomeric protein-encoding genes, is also caused by a defect in maintaining the quality of the ATP pool, which is an essential requirement for sarcomere function.


Subject(s)
Cardiomyopathies/enzymology , Growth Disorders/enzymology , Pyrophosphatases/physiology , Actins/genetics , Actins/metabolism , Adenosine Triphosphate/metabolism , Amino Acid Sequence , Animals , Cardiomyopathies/genetics , Cardiomyopathies/pathology , Female , Genotype , Growth Disorders/genetics , Growth Disorders/mortality , Inosine Nucleotides/metabolism , Male , Mice , Mice, Inbred C57BL , Mice, Knockout , Molecular Sequence Data , Myocardium/pathology , Phenotype , Pyrophosphatases/deficiency , Pyrophosphatases/genetics , RNA, Messenger/metabolism , Sarcomeres/metabolism , Sarcomeres/physiology , Weaning , Inosine Triphosphatase
6.
Cell Death Differ ; 16(3): 417-27, 2009 Mar.
Article in English | MEDLINE | ID: mdl-19008923

ABSTRACT

We examined the expression of galectin-1, an endogenous lectin with one carbohydrate-binding domain, in the adult mouse hippocampus after systemic kainate administration. We found that the expression of galectin-1 was remarkably increased in activated astrocytes of the CA3 subregion and dentate gyrus of the hippocampus, and in nestin-positive neural progenitors in the dentate gyrus. Quantitative reverse transcription PCR (RT-PCR) analysis revealed that the galectin-1 mRNA level in hippocampus began to increase 1 day after kainate administration and that a 13-fold increase was attained within 3 days. Western blotting analysis confirmed that the level of galectin-1 protein increased to more than three-fold a week after the exposure. We showed that isolated astrocytes express and secrete galectin-1. To clarify the significance of the increased expression of galectin-1 in hippocampus, we compared the levels of hippocampal cell proliferation in galectin-1 knockout and wild-type mice after saline or kainate administration. The number of 5-bromo-2'-deoxyuridine (BrdU)-positive cells detected in the subgranular zone (SGZ) of galectin-1 knockout mice decreased to 62% with saline, and to 52% with kainate, as compared with the number seen in the wild-type mice. Most of the BrdU-positive cells in SGZ expressed doublecortin and neuron-specific nuclear protein, indicating that they are immature neurons. We therefore concluded that galectin-1 promotes basal and kainate-induced proliferation of neural progenitors in the hippocampus.


Subject(s)
Cell Proliferation , Dentate Gyrus , Galectin 1/metabolism , Kainic Acid/metabolism , Neurons/physiology , Stem Cells/metabolism , Animals , Dentate Gyrus/cytology , Dentate Gyrus/metabolism , Galectin 1/genetics , Mice , Mice, Inbred C57BL , Mice, Knockout , Neurons/cytology , Stem Cells/cytology
7.
Clin Genet ; 73(6): 545-53, 2008 Jun.
Article in English | MEDLINE | ID: mdl-18422726

ABSTRACT

The present study was undertaken to elucidate germ line mutations of the base excision repair gene, MUTYH, in Japanese patients with adenomatous polyposis. We screened germ line mutations of adenomatous polyposis coli (APC) gene and MUTYH in 66 Japanese patients with adenomatous polyposis. APC was screened by the protein truncation test, while MUTYH was screened by polymerase chain reaction-based single-strand conformation polymorphism and direct sequencing. The nicking assay was applied in order to evaluate the DNA glycosylase activity of the identified MUTYH variant. In this study, Seven MUTYH variants were identified in 16 of 21 APC-negative patients. Q324H mutation was the most frequent mutation, with an allele frequency of 49%. Two patients carried biallelic mutations other than Q324H; a patient had biallelic G272E and A359V mutations, while the other had compound heterozygotes of P18L and G25D mutations. Nicking assay for G272E using the corresponding mouse MUTYH mutant with G257E revealed that G272E is a variant to cause an impaired DNA glycosylase activity. Homozygous MUTYH mutation accounts for approximately 10% of Japanese patients with adenomatous polyposis. G272E may be one of the mutations specific to patients with adenomatous polyposis in East Asia.


Subject(s)
Adenomatous Polyps/genetics , DNA Glycosylases/genetics , Mutation, Missense , Adenomatous Polyposis Coli/genetics , Adenomatous Polyps/epidemiology , Asian People , DNA Glycosylases/physiology , DNA Mutational Analysis , Genomics , Humans
8.
Cell Death Differ ; 14(4): 716-26, 2007 Apr.
Article in English | MEDLINE | ID: mdl-17170753

ABSTRACT

Elongin A is a transcription elongation factor that increases the overall rate of mRNA chain elongation by RNA polymerase II. To gain more insight into the physiological functions of Elongin A, we generated Elongin A-deficient mice. Elongin A homozygous mutant (Elongin A(-/-)) embryos demonstrated a severely retarded development and died at between days 10.5 and 12.5 of gestation, most likely due to extensive apoptosis. Moreover, mouse embryonic fibroblasts (MEFs) derived from Elongin A(-/-) embryos exhibited not only increased apoptosis but also senescence-like growth defects accompanied by the activation of p38 MAPK and p53. Knockdown of Elongin A in MEFs by RNA interference also dramatically induced the senescent phenotype. A study using inhibitors of p38 MAPK and p53 and the generation of Elongin A-deficient mice with p53-null background suggests that both the p38 MAPK and p53 pathways are responsible for the induction of senescence-like phenotypes, whereas additional signaling pathways appear to be involved in the mediation of apoptosis in Elongin A(-/-) cells. Taken together, our results suggest that Elongin A is required for the transcription of genes essential for early embryonic development and downregulation of its activity is tightly associated with cellular senescence.


Subject(s)
Apoptosis/genetics , Cellular Senescence/genetics , Transcription Factors/genetics , Transcriptional Elongation Factors/genetics , Transcriptional Elongation Factors/metabolism , Animals , Elongin , Female , Fetal Death/genetics , Fetus/abnormalities , Fibroblasts/cytology , Gene Expression Regulation, Developmental/genetics , Immunohistochemistry , Mice , Mice, Inbred C57BL , Mice, Knockout , Pregnancy , Tumor Suppressor Protein p53/metabolism , p38 Mitogen-Activated Protein Kinases/metabolism
9.
Neurology ; 66(11): 1672-8, 2006 Jun 13.
Article in English | MEDLINE | ID: mdl-16769939

ABSTRACT

OBJECTIVE: To determine the clinical and radiologic features of Gerstmann-Sträussler-Scheinker syndrome caused by Pro102Leu mutation in PRNP (GSS102). METHODS: The authors report 11 patients (nine families) with clinically and radiologically diagnosed GSS102. RESULTS: All patients showed mild gait disturbance, dysesthesia and hyporeflexia of the lower legs, and truncal ataxia, and 9 of 11 patients showed proximal leg muscle weakness during the early stage of the disease. Dementia was not a main symptom during the early stage. Brain MRI and EEG abnormalities were not prominent initially. SPECT (N-isopropyl-p-[(123)I]iodoamphetamine) analyzed by the three-dimensional stereotactic surface projection (SSP) method detected abnormalities in five patients early during the course of the illness. SPECT findings showed diffusely decreased cerebral blood flow, demonstrated by a mosaic pattern, with the lowest perfusion noted in the occipital lobes. In contrast, blood flow to the cerebellum was preserved. These studies suggested sites of pathology in GSS102, with the main lesions probably located in the cerebrum and the spinal cord (posterior horn and spinocerebellar tract) instead of the cerebellum. CONCLUSIONS: Key features for early diagnosis of Gerstmann-Sträussler-Scheinker syndrome caused by Pro102Leu mutation in PRNP (GSS102) are truncal ataxia, dysesthesia and hyporeflexia of the lower legs, and mild dysarthria. Normal cerebellar MRI and abnormal cerebral SPECT findings are characters of early GSS102.


Subject(s)
Ataxia/diagnosis , Diagnostic Imaging/methods , Dysarthria/diagnosis , Gait Disorders, Neurologic/diagnosis , Gerstmann-Straussler-Scheinker Disease/diagnosis , Hyperalgesia/diagnosis , Amyloid/genetics , Ataxia/genetics , Child, Preschool , Diagnosis, Differential , Dysarthria/genetics , Female , Gait Disorders, Neurologic/genetics , Genetic Predisposition to Disease/genetics , Gerstmann-Straussler-Scheinker Disease/genetics , Humans , Hyperalgesia/genetics , Infant , Male , Prion Proteins , Prions , Protein Precursors/genetics , Reflex, Abnormal/genetics
10.
Cell Death Differ ; 13(4): 551-63, 2006 Apr.
Article in English | MEDLINE | ID: mdl-16273081

ABSTRACT

We previously reported that 8-oxoguanine (8-oxoG) accumulates in the cytoplasm of dopamine neurons in the substantia nigra of patients with Parkinson's disease and the expression of MTH1 carrying an oxidized purine nucleoside triphosphatase activity increases in these neurons, thus suggesting that oxidative damage in nucleic acids is involved in dopamine neuron loss. In the present study, we found that levels of 8-oxoG in cellular DNA and RNA increased in the mouse nigrostriatal system during the tyrosine hydroxylase (TH)-positive dopamine neuron loss induced by the administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). MTH1-null mice exhibited a greater accumulation of 8-oxoG in mitochondrial DNA accompanied by a more significant decrease in TH and dopamine transporter immunoreactivities in the striatum after MPTP administration, than in wild-type mice. We thus demonstrated that MTH1 protects the dopamine neurons from oxidative damage in the nucleic acids, especially in the mitochondrial DNA of striatal nerve terminals of dopamine neurons.


Subject(s)
1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine , DNA, Mitochondrial/metabolism , Dopamine/metabolism , Guanine/analogs & derivatives , Neurons/enzymology , Parkinsonian Disorders/enzymology , Phosphoric Monoester Hydrolases/metabolism , Animals , Corpus Striatum/enzymology , Corpus Striatum/pathology , DNA Repair Enzymes/deficiency , DNA Repair Enzymes/genetics , Disease Models, Animal , Dopamine Plasma Membrane Transport Proteins/metabolism , Guanine/metabolism , Male , Mice , Mice, Inbred C57BL , Mice, Knockout , Neurons/pathology , Oxidative Stress , Parkinsonian Disorders/chemically induced , Parkinsonian Disorders/pathology , Phosphoric Monoester Hydrolases/deficiency , Phosphoric Monoester Hydrolases/genetics , RNA/metabolism , Substantia Nigra/enzymology , Substantia Nigra/pathology , Tyrosine 3-Monooxygenase/metabolism
11.
Cell Death Differ ; 12(8): 1078-96, 2005 Aug.
Article in English | MEDLINE | ID: mdl-15861185

ABSTRACT

Transient forebrain ischemia causes selective induction of DeltaFosB, an AP-1 (activator protein-1) subunit, in cells within the ventricle wall or those in the dentate gyrus in the rat brain prior to neurogenesis, followed by induction of nestin, a marker for neuronal precursor cells, or galectin-1, a beta-galactoside sugar-binding lectin. The adenovirus-mediated expression of FosB or DeltaFosB induced expression of nestin, glial fibrillary acidic protein and galectin-1 in rat embryonic cortical cells. DeltaFosB-expressing cells exhibited a significantly higher survival and proliferation after the withdrawal of B27 supplement than the control or FosB-expressing cells. The decline in the DeltaFosB expression in the survivors enhanced the MAP2 expression. The expression of DeltaFosB in cells within the ventricle wall of the rat brain also resulted in an elevated expression of nestin. We therefore conclude that DeltaFosB can promote the proliferation of quiescent neuronal precursor cells, thus enhancing neurogenesis after transient forebrain ischemia.


Subject(s)
Brain/metabolism , Galectin 1/physiology , Ischemic Attack, Transient/metabolism , Proto-Oncogene Proteins c-fos/physiology , Transcription Factors/physiology , Adenoviridae/genetics , Animals , Cells, Cultured , Cerebral Cortex/metabolism , Embryo, Mammalian , Galectin 1/biosynthesis , Glial Fibrillary Acidic Protein/biosynthesis , Immunohistochemistry , Intermediate Filament Proteins/biosynthesis , Male , Mice , Microscopy, Confocal , Microscopy, Fluorescence , Nerve Tissue Proteins/biosynthesis , Nestin , Neurons/cytology , Neurons/metabolism , Proto-Oncogene Proteins c-fos/biosynthesis , Proto-Oncogene Proteins c-fos/genetics , Rabbits , Rats , Rats, Inbred SHR , Reverse Transcriptase Polymerase Chain Reaction , Transcription Factors/biosynthesis , Transcription Factors/genetics
12.
Cell Death Differ ; 11(10): 1076-83, 2004 Oct.
Article in English | MEDLINE | ID: mdl-15181456

ABSTRACT

We previously identified a novel N-terminally processed form of galectin-1, galectin-1beta (Gal-1beta) whose expression was induced by DeltaFosB. In the present study, the biochemical properties and biological functions of Gal-1beta were compared with the full-length form of galectin-1 (Gal-1alpha). We first purified recombinant mouse Gal-1alpha and beta (rmGal-1alpha, beta) to near homogeneity. The rmGal-1alpha exists as a monomer under oxidized conditions and forms a dimer under reduced conditions, while the rmGal-1beta exists as a monomer regardless of redox conditions. The affinity of rmGal-1beta to beta-lactose was approximately two-fold lower than that of rmGal-1alpha under reduced conditions. The viability of Jurkat cells efficiently decreased when they were exposed to rmGal-1alpha, however, rmGal-1beta barely induced such a reduction. In contrast, both rmGal-1alpha and rmGal-1beta exhibited an equivalent capacity to promote axonal regeneration from the dorsal root ganglion explants. Our results suggest that the biochemical properties of rmGal-1beta determine its biological functions.


Subject(s)
Axons/drug effects , Axons/metabolism , Galectin 1/chemistry , Galectin 1/pharmacology , Nerve Regeneration/drug effects , Animals , Cell Death/drug effects , Circular Dichroism , Dimerization , Galectin 1/genetics , Galectin 1/metabolism , Ganglia, Spinal/cytology , Ganglia, Spinal/drug effects , Ganglia, Spinal/metabolism , Humans , Jurkat Cells , Lectins/pharmacology , Mice , Models, Molecular , Oxidation-Reduction , Protein Structure, Secondary , Protein Structure, Tertiary , Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization , Structure-Activity Relationship
14.
Cell Death Differ ; 10(5): 496-507, 2003 May.
Article in English | MEDLINE | ID: mdl-12728248

ABSTRACT

The fates of Rat1a cells expressing FosB and DeltaFosB as fusion proteins (ER-FosB, ER-DeltaFosB) with the ligand binding domain of human estrogen receptor were examined. The binding of estrogen to the fusion proteins resulted in their nuclear translocation and triggered cell proliferation, and thereafter delayed cell death was observed only in cells expressing ER-DeltaFosB. The proliferation of Rat1a cells, but not cell death triggered by ER-DeltaFosB, was completely abolished by butyrolactone I, an inhibitor of cycline-dependent kinases, and was partly suppressed by antisense oligonucleotides against galectin-1, whose expression is induced after estrogen administration. The cell death was accompanied by the activation of caspase-3 and -9, the fragmentation of the nuclear genome and cytochrome c release from the mitochondria, and was suppressed by zDEVD-fmk and zLEHD-fmk but not zIETD-fmk. The cell death was not suppressed by exogenous His-PTD-Bcl-x(L) at all, suggesting involvement of a Bcl-x(L)-resistant pathway for cytochrome c release.


Subject(s)
Apoptosis/physiology , Embryo, Mammalian/metabolism , Proto-Oncogene Proteins c-fos/metabolism , Animals , Apoptosis/drug effects , Apoptosis/genetics , Blotting, Western , Caspases/metabolism , Cell Division/drug effects , Cell Division/genetics , Cell Division/physiology , Cell Line , Cytochromes c/metabolism , DNA Fragmentation/drug effects , Embryo, Mammalian/cytology , Embryo, Mammalian/ultrastructure , Estrogens/pharmacology , Galectin 1/genetics , Galectin 1/metabolism , Gene Expression Regulation/drug effects , Humans , Microscopy, Electron , Protein Isoforms/genetics , Protein Isoforms/metabolism , Proto-Oncogene Proteins c-fos/genetics , Rats , Receptors, Estrogen/genetics , Receptors, Estrogen/metabolism , Recombinant Fusion Proteins/genetics , Recombinant Fusion Proteins/metabolism , Time Factors
15.
Br J Cancer ; 88(4): 521-9, 2003 Feb 24.
Article in English | MEDLINE | ID: mdl-12592365

ABSTRACT

Inactivations of DNA repair genes, O(6)-methylguanine-DNA methyltransferase (MGMT) and hMLH1, by promoter hypermethylation have been reported in several types of primary human neoplasia. This epigenetic inactivation mechanism remains elusive in hepatocellular carcinoma (HCC). To investigate the relation between the expression of MGMT and hMLH1 and the CpG methylation within their promoters in HCCs with or without hepatitis viral infection, we performed immunohistochemistry and urea/bisulphite sequencing on 46 HCCs, corresponding noncancerous tissues, and 20 normal liver tissues. MGMT- and hMLH1-negative HCCs were 60.9% (28 out of 46) and 21.8% (10 out of 46), respectively. HCCs lacking both proteins were 10.9% (five out of 46). The frequency and extent of CpG methylation in the MGMT promoter increased along with hepatitis viral infection and pathological progression. MGMT-negative tumours showed very frequent and widespread methylation in the promoter compared with MGMT-positive tumours. Half of the hMLH1-negative HCCs showed promoter hypermethylation. These data suggested that MGMT gene silencing in a subset of HCCs was likely caused by epigenetic alteration, such as promoter hypermethylation, and that the promoter hypermethylation silenced the hMLH1 gene in half of the hMLH1-negative tumours. A correlation between the promoter methylation status and viral infection, although it was weak, intimated that hepatitis viral infections could play a role in the CpG methylation of the MGMT promoter.


Subject(s)
Carcinoma, Hepatocellular/complications , Carcinoma, Hepatocellular/genetics , CpG Islands/genetics , DNA Methylation , Hepatitis, Viral, Human/complications , Hepatitis, Viral, Human/genetics , Neoplasm Proteins/genetics , O(6)-Methylguanine-DNA Methyltransferase/genetics , Promoter Regions, Genetic/genetics , Adaptor Proteins, Signal Transducing , Aged , Carcinoma, Hepatocellular/pathology , Carrier Proteins , Female , Gene Expression Regulation, Neoplastic , Humans , Immunohistochemistry , Liver/metabolism , Male , Middle Aged , MutL Protein Homolog 1 , Neoplasm Proteins/analysis , Neoplasm Staging , Nuclear Proteins , O(6)-Methylguanine-DNA Methyltransferase/analysis , Polymerase Chain Reaction
16.
Clin Nucl Med ; 26(12): 1028-31, 2001 Dec.
Article in English | MEDLINE | ID: mdl-11711707

ABSTRACT

A 17-year-old girl with hereditary multiple exostoses, who was thought to have malignant transformation of an exostotic lesion, was examined by bone and Tl-201 chloride scintigraphy. Scintigraphy showed markedly intense uptake by the lesion, whereas Tl-201 imaging did not. Bone scintigraphy revealed intense to moderate uptake in other exostotic lesions, but none was apparent on the Tl-201 study. The lesion was resected and the histopathologic diagnosis was osteochondroma. Negative findings of Tl-201 scintigraphy may not exclude the possibility of chondrosarcoma, and the utility of this method may be limited. However, Tl-201 scintigraphy appears to have a useful role in differentiating malignant transformation from benign osteochondroma in hereditary multiple exostoses.


Subject(s)
Bone and Bones/diagnostic imaging , Exostoses, Multiple Hereditary/diagnostic imaging , Thallium Radioisotopes , Thallium , Adolescent , Bone Neoplasms/diagnostic imaging , Chondrosarcoma/diagnostic imaging , Diagnosis, Differential , Female , Humans , Radionuclide Imaging
17.
Neuroreport ; 12(13): 2895-9, 2001 Sep 17.
Article in English | MEDLINE | ID: mdl-11588598

ABSTRACT

The oxidized purine nucleoside triphosphatase, hMTH1, has a critical role towards preventing errors caused by oxidized purine nucleoside triphosphates such as 8-oxo-dGTP and 2-hydroxy-dATP. We investigated the immunohistochemical expression of hMTH1 in human hippocampal postmortem tissues representing non-neurological disease and Alzheimer's disease (AD). In the non-neurological subjects the hMTH1 protein was enriched in the stratum lucidum at CA3 corresponding to mossy fiber synapses. In AD subjects, the synaptic immunoreactivities at CA3 were significantly decreased, whereas they tended to be increased at the entorhinal cortex. We suggest that the expression of hMTH1 indicates indirect evidence of oxidative stress and its regulation is regionally differentiated in AD.


Subject(s)
Alzheimer Disease/enzymology , DNA Repair Enzymes , Gene Expression Regulation, Enzymologic/physiology , Mossy Fibers, Hippocampal/enzymology , Oxidative Stress/physiology , Phosphoric Monoester Hydrolases/metabolism , Purines/metabolism , Aged , Aged, 80 and over , Alzheimer Disease/pathology , Alzheimer Disease/physiopathology , Female , Humans , Immunohistochemistry , Male , Middle Aged , Mossy Fibers, Hippocampal/pathology , Mossy Fibers, Hippocampal/physiopathology
18.
Proc Natl Acad Sci U S A ; 98(20): 11456-61, 2001 Sep 25.
Article in English | MEDLINE | ID: mdl-11572992

ABSTRACT

Oxygen radicals, which can be produced through normal cellular metabolism, are thought to play an important role in mutagenesis and tumorigenesis. Among various classes of oxidative DNA damage, 8-oxo-7,8-dihydroguanine (8-oxoG) is most important because of its abundance and mutagenicity. The MTH1 gene encodes an enzyme that hydrolyzes 8-oxo-dGTP to monophosphate in the nucleotide pool, thereby preventing occurrence of transversion mutations. By means of gene targeting, we have established MTH1 gene-knockout cell lines and mice. When examined 18 months after birth, a greater number of tumors were formed in the lungs, livers, and stomachs of MTH1-deficient mice, as compared with wild-type mice. The MTH1-deficient mouse will provide a useful model for investigating the role of the MTH1 protein in normal conditions and under oxidative stress.


Subject(s)
DNA Repair Enzymes , Phosphoric Monoester Hydrolases/genetics , Adenocarcinoma/genetics , Alleles , Animals , Blastocyst , Blotting, Western , Chimera , Clone Cells , Crosses, Genetic , DNA Damage , DNA Primers , Exons , Female , Liver/enzymology , Lung Neoplasms/genetics , Male , Mice , Mice, Inbred C57BL , Recombination, Genetic , Restriction Mapping , Stomach Neoplasms/genetics
19.
Article in English | MEDLINE | ID: mdl-11554314

ABSTRACT

In mammalian cells, more than one genome has to be maintained throughout the entire life of the cell, one in the nucleus and the other in mitochondria. It seems likely that the genomes in mitochondria are highly exposed to reactive oxygen species (ROS) as a result of their respiratory function. Human MTH1 (hMTH1) protein hydrolyzes oxidized purine nucleoside triphosphates, such as 8-oxo-dGTP, 8-oxo-dATP, and 2-hydroxy (OH)-dATP, thus suggesting that these oxidized nucleotides are deleterious for cells. Here, we report that a single-nucleotide polymorphism (SNP) in the human MTH1 gene alters splicing patterns of hMTH1 transcripts, and that a novel hMTH1 polypeptide with an additional mitochondrial targeting signal is produced from the altered hMTH1 mRNAs; thus, intracellular location of hMTH1 is likely to be affected by a SNP. These observations strongly suggest that errors caused by oxidized nucleotides in mitochondria have to be avoided in order to maintain the mitochondrial genome, as well as the nuclear genome, in human cells. Based on these observations, we further characterized expression and intracellular localization of 8-oxoG DNA glycosylase (hOGG1) and 2-OH-A/adenine DNA glycosylase (hMYH) in human cells. These two enzymes initiate base excision repair reactions for oxidized bases in DNA generated by direct oxidation of DNA or by incorporation of oxidized nucleotides. We describe the detection of the authentic hOGG1 and hMYH proteins in mitochondria, as well as nuclei in human cells, and how their intracellular localization is regulated by alternative splicing of each transcript.


Subject(s)
Cell Nucleus/enzymology , DNA Glycosylases , DNA Repair , Fungal Proteins/physiology , Guanine/analogs & derivatives , Membrane Proteins , Mitochondria/enzymology , N-Glycosyl Hydrolases/physiology , Saccharomyces cerevisiae Proteins , Adaptor Proteins, Signal Transducing , Amino Acid Sequence , Animals , Cell Compartmentation , DNA Damage , DNA, Mitochondrial/chemistry , DNA, Mitochondrial/genetics , DNA-Formamidopyrimidine Glycosylase , Fungal Proteins/analysis , Guanine/metabolism , HeLa Cells , Humans , Molecular Sequence Data , N-Glycosyl Hydrolases/analysis , Oxidants/toxicity , Oxidation-Reduction , Oxidative Stress , Point Mutation , Polymorphism, Genetic , Protein Sorting Signals/genetics , Protein Sorting Signals/physiology , Protein Transport , Purine Nucleosides/metabolism , RNA Splicing , RNA, Messenger/genetics , RNA, Messenger/metabolism , Sequence Alignment , Sequence Homology, Amino Acid , Species Specificity , Transfection
20.
Psychol Med ; 31(6): 1079-88, 2001 Aug.
Article in English | MEDLINE | ID: mdl-11513375

ABSTRACT

BACKGROUND: Motor skill learning may be impaired in schizophrenia. While functional brain imaging studies have shown reduced activation during motor task performance in schizophrenic patients, brain activity changes with motor skill learning in these patients have not been studied by functional imaging. METHODS: A sequential complex motor task involving the right hand was performed by nine medicated schizophrenic patients and 10 age-matched healthy controls. Functional magnetic resonance images were obtained using a gradient echo, echoplanar imaging (EPI) pulse sequence before and after 1 week of training in performing the task. RESULTS: Bilaterally, patients showed significantly less blood oxygenation level-dependent (BOLD) signal response in the premotor area (PMA) before beginning motor training than controls. BOLD signal response increased in the left PMA of schizophrenic patients after 1 week of motor training; in contrast, the signal decreased in the left PMA of control subjects. Training effects concerning the number of finger movement sequences achieved did not differ between groups. Daily neuroleptic dose did not significantly affect changes with training in BOLD signal response in the PMA. CONCLUSIONS: These preliminary results suggest that schizophrenic patients have dysfunction of neural networks in areas including the PMA that are involved in executing a complex motor task. In terms of brain activity, motor learning may be less efficient or slower in the patients than in healthy subjects.


Subject(s)
Brain/physiopathology , Learning/physiology , Magnetic Resonance Imaging , Psychomotor Disorders/etiology , Schizophrenia/complications , Schizophrenia/physiopathology , Adolescent , Adult , Brain/pathology , Female , Functional Laterality/physiology , Humans , Male , Psychomotor Disorders/diagnosis , Severity of Illness Index
SELECTION OF CITATIONS
SEARCH DETAIL
...