Biomedical subjects

Takuya Ueda

Publications and source records attributed to Takuya Ueda.

12 recordsLinked to original sources

PubMed2003

Down-regulation of the mitochondrial translation system during terminal differentiation of HL-60 cells by 12-O-tetradecanoyl-1-phorbol-13-acetate: comparison with the cytoplasmic translation system.

Mitochondrial (mt) biogenesis depends on both the nuclear and mt genomes, and a coordination of these two genetic systems is necessary for proper cell functioning. Little is known about the regulatory mechanisms of mt translation or about the expression of mt translation factors. Here, we studied the expression of mt translation factors during 12-O-tetradecanoyl-1-phorbol-13-acetate (TPA)-induced terminal differentiation of HL-60 cells. For all mt translation factors investigated, mRNA expression was markedly down-regulated in a coordinate and specific manner, whereas mRNA levels for the cytoplasmic translation factors showed only a slight reduction. An actinomycin D chase study and nuclear run-on assay revealed that the TPA-induced decrease in mt elongation factor Tu (EF-Tumt) mRNA mainly results from decreased mRNA stability. Polysome analysis showed that there was no significant translational control of mt translation factor (EF-Tumt, ribosomal proteins L7/L12mt and S12mt) mRNA expression during differentiation. Thus, the decreased protein level of one of these mt translation factors (EF-Tumt) simply reflects its decreased mRNA level. It was also demonstrated by pulse labeling of mt translation products that the down-regulation of mt translational activity is actually associated with down-regulated mt translation factor expression during cellular differentiation. Our results illustrate that the regulatory mechanisms of mt translational activity upon terminal differentiation (in response to the growth arrest) is different to that of the cytoplasmic system, where the control of mRNA translational efficiency of major translation factors is the central mechanism for their down-regulation.

Blotting, Northern↗

PubMed2003

A point mutation in ribosomal protein L7/L12 reduces its ability to form a compact dimer structure and to assemble into the GTPase center.

An Escherichia coli mutant, LL103, harboring a mutation (Ser15 to Phe) in ribosomal protein L7/L12 was isolated among revertants of a streptomycin-dependent strain. In the crystal structure of the L7/L12 dimer, residue 15 within the N-terminal domain contacts the C-terminal domain of the partner monomer. We tested effects of the mutation on molecular assembly by biochemical approaches. Gel electrophoretic analysis showed that the Phe15-L7/L12 variant had reduced ability in binding to L10, an effect enhanced in the presence of 0.05% of nonionic detergent. Mobility of Phe15-L7/L12 on gel containing the detergent was very low compared to the wild-type proteins, presumably because of an extended structural state of the mutant L7/L12. Ribosomes isolated from LL103 cells contained a reduced amount of L7/L12 and showed low levels (15-30% of wild-type ribosomes) of activities dependent on elongation factors and in translation of natural mRNA. The ribosomal activity was completely recovered by addition of an excess amount of Phe15-L7/L12 to the ribosomes, suggesting that the mutant L7/L12 exerts normal functions when bound on the ribosome. The interaction of Ser15 with the C-terminal domain of the partner molecule seems to contribute to formation of the compact dimer structure and its efficient assembly into the ribosomal GTPase center. We propose a model relating compact and elongated forms of L7/L12 dimers. Phe15-L7/L12 provides a new tool for studying the functional structure of the homodimer.

Amino Acid Sequence↗

PubMed2003

Decreased CCA-addition in human mitochondrial tRNAs bearing a pathogenic A4317G or A10044G mutation.

Pathogenic point mutations in mitochondrial tRNA genes are known to cause a variety of human mitochondrial diseases. Reports have associated an A4317G mutation in the mitochondrial tRNA(Ile) gene with fatal infantile cardiomyopathy and an A10044G mutation in the mitochondrial tRNA(Gly) gene with sudden infant death syndrome. Here we demonstrate that both mutations inhibit in vitro CCA-addition to the respective tRNA by the human mitochondrial CCA-adding enzyme. Structures of these two mutant tRNAs were examined by nuclease probing. In the case of the A4317G tRNA(Ile) mutant, structural rearrangement of the T-arm region, conferring an aberrantly stable T-arm structure and an increased T(m) value, was clearly observed. In the case of the A10044G tRNA(Gly) mutant, high nuclease sensitivity in both the T- and D-loops suggested a weakened interaction between the loops. These are the first reported instances of inefficient CCA-addition being one of the apparent molecular pathogeneses caused by pathogenic point mutations in human mitochondrial tRNA genes.

DNA, Mitochondrial↗

PubMed2003

A novel screening system for self-mRNA targeting proteins.

Here we describe the application of an in vitro translation system for genetic screening, to identify RNA-binding proteins that bind to their own mRNAs. It is a relatively novel system designed using an advanced cell-free translation system reconstructed with purified translational components. Due to the absence of nucleases and proteases, the complex of mRNA and nascent polypeptide synthesized in this system is expected to exhibit high stability ensuring the following efficient selection toward the protein. Escherichia coli ribosomal protein S15, which is known to bind to its own mRNA, was employed as a model molecule to evaluate the system. Wild-type S15 mRNA specifically isolated from a mutant mRNA lacking the secondary structure responsible for binding the S15 protein accumulated markedly after several rounds of selection-amplification. The success of this selection demonstrates the potentiality of the systematic screening of self-mRNA targeting proteins through direct and functional selection. This strategy as a method to identify peptides or proteins that bind to their own mRNAs, is of general interest and has different potential applications, such as, the identification of new regulatory proteins or peptide motifs for RNA recognition, the study of self-mRNA-protein interactions, etc.

Amino Acid Motifs↗

PubMed2002

Chondrosarcoma of the nasal septum.

The nasal septum is a particularly rare site of origin of chondrosarcoma. Cranial base invasion may be at hand, with such lesions making complete tumor removal difficult. MRI techniques allow precise definition of tumor extent. In the described case, CT and Dynamic MR imaging were performed in a case of chondrosarcoma of the nasal septum. Imaging clearly illustrated size and extent of the mass with central regions of internal calcification. Dynamic MRI was additionally performed, which helped to define the presumed origin of the lesion from the nasal septum.

Adult↗

PubMed2002

The role of SmpB protein in trans-translation.

The function of SmpB protein in the trans-translation system was evaluated using the well-defined cell-free translation system consisting of purified ribosome, alanyl-tRNA synthetase and elongation factors. The analysis showed that SmpB protein enhances alanine-accepting activity of tmRNA and that SmpB protein and tmRNA are sufficient to complete the trans-translation process in the presence of translational components. Moreover, SmpB is indispensable in the addition of tag-peptide onto ribosomes by tmRNA. In particular, the A-site binding of tmRNA is inhibited in the absence of SmpB.

Alanine↗

PubMed2002

Dynamic-enhanced MRI predicts metastatic potential of invasive ductal breast cancer.

BACKGROUND: Dynamic magnetic resonance imaging (MRI) has improved the detection of breast malignancies. The method is based on estimating the velocity of contrast enhancement taking into account increased angiogenesis in tumor. Microvessel density correlates with breast carcinoma metastasis. Thus, we hypothesized that contrast enhancement on MRI correlates with metastasis in breast cancer patients. The present study attempts to clarify the quantitative assessment of dynamic data, and examines the correlation between MRI enhancement and breast carcinoma metastasis. METHODS: The subjects consisted of 31 patients with invasive ductal breast cancer. Twenty patients were disease free for five years (group A), and eleven patients suffered from metastatic disease at distant sites concurrently or postoperatively (group B). Dynamic MRI was performed preoperatively using a 1.5T system in all cases. Using the dynamic data, the signal intensity (SI)ratio and SI index were determined and analyzed retrospectively taking into account the presence of distant metastases. RESULTS: The values of the SI ratio were 2.2+/-0.7 in group A and 2.3+/-0.4 in group B, respectively, with no significant difference seen between the groups. The SI index value was significantly higher in group B (28.5+/-32.8) than in group A (10.3+/-5.5, p<0.05). CONCLUSIONS: The current series suggests that the SI index could distinguish patients with high risk of distant metastasis from disease free patients, preoperatively. If a suitable borderline value were established, the quantitative dynamic parameter determined by MRI may be useful for predicting the prognosis of breast cancer patients.

Adult↗

PubMed2002

The cephalopod Loligo bleekeri mitochondrial genome: multiplied noncoding regions and transposition of tRNA genes.

We previously reported the sequence of a 9260-bp fragment of mitochondrial (mt) DNA of the cephalopod Loligo bleekeri [J. Sasuga et al. (1999) J. Mol. Evol. 48:692-702]. To clarify further the characteristics of Loligo mtDNA, we have sequenced an 8148-bp fragment to reveal the complete mt genome sequence. Loligo mtDNA is 17,211 bp long and possesses a standard set of metazoan mt genes. Its gene arrangement is not identical to any other metazoan mt gene arrangement reported so far. Three of the 19 noncoding regions longer than 10 bp are 515, 507, and 509 bp long, and their sequences are nearly identical, suggesting that multiplication of these noncoding regions occurred in an ancestral Loligo mt genome. Comparison of the gene arrangements of Loligo, Katharina tunicata, and Littorina saxatilis mt genomes revealed that 17 tRNA genes of the Loligo mt genome are adjacent to noncoding regions. A majority (15 tRNA genes) of their counterparts is found in two tRNA gene clusters of the Katharina mt genome. Therefore, the Loligo mt genome (17 tRNA genes) may have spread over the genome, and this may have been coupled with the multiplication of the noncoding regions. Maximum likelihood analysis of mt protein genes supports the clade Mollusca + Annelida + Brachiopoda but fails to infer the relationships among Katharina, Loligo, and three gastropod species.

Animals↗

PubMed2002

tRNA recognition by CCA-adding enzyme.

The CCA-adding enzyme [ATP (CTP): tRNA nucleotidyltransferase (EC. 2.7.7.25)] catalyzes the addition of the conserved CCA sequence to the 3'-terminus of tRNAs. It is known that CCA-adding enzymes from all three kingdoms recognize the elbow region of L-shape tRNA formed by the tertiary interaction between T-loop and D-loop. We here demonstrate that C. elegans mitochondrial CCA-adding enzyme has broad substrate specificity toward nematode mitochondrial tRNAs which lack entire T- or D-arms, by cloning and characterizing the recombinant protein.

Animals↗

PubMed2002

Diffuse pulmonary involvement by mycosis fungoides: high-resolution computed tomography and pathologic findings.

The authors report the high-resolution computed tomography (HRCT) appearance of diffuse pulmonary involvement by mycosis fungoides in a 74-year-old woman whose clinical and radiographic manifestations simulated pneumonia. The HRCT showed multiple, dense, peribronchovascular nodules with surrounding ground-glass opacity and several wedge-shape peripheral opacities. The autopsy specimen revealed angiocentric and peribronchovascular involvement of mycosis fungoides and pulmonary infarctions distal to angiocentric infiltration of the tumor cells.

Aged↗

PubMed2002

Induction of chromatin damage and distribution of isochromatid breaks in human fibroblast cells exposed to heavy ions.

The frequency of chromatid breaks and the distribution of isochromatid breaks were measured in G2-phase normal human fibroblasts prematurely condensed a short time after exposure to low- or high-LET radiations. The average number of isochromatid breaks from a single particle traversal increased with increasing LET values, while the average number of chromatid-type breaks appeared to reach a plateau. The distribution of isochromatid breaks after high-LET iron particles exposure was overdispersed compared to gamma-rays, indicating that a single iron particle traversal through a cell nucleus can produce multiple isochromatid breaks.

Chromatids↗

PubMedDate not supplied

Sclerosing lipogranuloma of male genitalia: CT and MR images.

We report the imaging findings of sclerosing lipogranuloma. Sclerosing lipogranuloma is a peculiar granulomatous fatty tissue reaction. The majority of the cases occur in the genital and urinary tracts. To our knowledge, the CT and MR images of this rare entity have not been reported in the English literature. We present a case that was suspected to be sclerosing lipogranuloma of the male genitalia on CT and MR images and was diagnosed by open biopsy.

Granuloma↗