Biomedical subjects

Tomoaki Ando

Publications and source records attributed to Tomoaki Ando.

25 records · Page 2Linked to original sources

PubMed2003

Escherichia coli tRNAs are resistant to the hyperprocessing reaction of homologous E. coli ribonuclease P ribozyme.

Bacterial ribonuclease P RNA ribozyme can do the hyperprocessing reaction, the internal cleavage reaction of some floppy eukaryotic tRNAs. The hyperprocessing reaction can be used as a detection tool to examine the stability of the cloverleaf shape of tRNA. Until now, the hyperprocessing reaction has been observed in the heterologous combination of eukaryotic tRNAs and bacterial RNase P enzymes. In this paper, we examined the hyperprocessing reaction of Escherichia coli tRNAs by homologous E. coli RNase P, to find that these homologous tRNAs were resistant to the toxic hyperprocessing reaction. Our results display the evidence for molecular co-evolution between homologous tRNAs and RNase P in the bacterium E. coli.

Bacillus subtilis↗

PubMed2003

Comparative analyses of hairpin substrate recognition by Escherichia coli and Bacillus subtilis ribonuclease P ribozymes.

Previously, we reported that the substrate shape recognition of the Escherichia coli ribonuclease (RNase) P ribozyme depends on the concentration of magnesium ion in vitro. We additionally examined the Bacillus subtilis RNase P ribozyme and found that the B. subtilis enzyme also required high magnesium ion, above 10 mM, for cleavage of a hairpin substrate. The results of kinetic studies showed that the metal ion concentration affected both the catalysis and the affinity of the ribozymes toward a hairpin RNA substrate.

Bacillus subtilis↗

PubMed2003

The protein component of bacterial ribonuclease P flickers the metal ion response to the substrate shape preference of the ribozyme.

The substrate shape specificity of the Escherichia coli ribonuclease P (RNase P) ribozyme depends on the concentration of magnesium ion. At 10 mM or more, it can cleave a hairpin substrate as well as a cloverleaf pre-transfer RNA (tRNA). The results showed, however, that the holo enzyme cleaved the hairpin substrate at low concentrations of magnesium ion. Considering that the homologous E. coli tRNAs are resistant to internal cleavage by the RNase P, the phenomena suggest that this catalytic activity might take part in the removing the mis-folded RNAs in the cell.

Catalysis↗

PubMed2002

Cdc25C interacts with PCNA at G2/M transition.

Cdc25 activates maturation promoting factor (MPF) and promotes mitosis by removing the inhibitory phosphate from the Tyr-15 of Cdc2 in human cells. In this study, we searched the interacting protein(s) of human Cdc25C using the yeast two-hybrid screen and identified proliferating cell nuclear antigen (PCNA) as an interacting partner of Cdc25C. The interaction between Cdc25C and PCNA was confirmed in vitro and in vivo. Co-immunoprecipitation analyses using human T cell line, Jurkat, further revealed that Cdc25C interacted with PCNA transiently when cells began to enter mitosis. Immunofluorescence analysis also showed that Cdc25C and PCNA were transiently co-localized in the nucleus at the beginning of M phase. Together with the previous observations of the interaction between various cdc/cyclin and PCNA, our findings strongly suggested a potential role of PCNA at the G2 to M phase transition of cell cycle.

Cell Cycle Proteins↗

PubMed2002

Regulation of bacterial RNase P ribozyme reaction by divalent cation and guide DNA.

The RNA subunit of bacterial ribonuclease P (RNase P) is a ribozyme which can cleave a canonical cloverleaf tRNA precursor and a hairpin RNA with a CCA-3' tag sequence as its substrate. With high concentration of Mg ion, the ribozyme as well as holo enzyme internally cleaves certain tRNAs in vitro. We denoted this unusual reaction as hyperprocessing. By controlling magnesium ion concentration for the reaction and also by forcing the RNA shape with external guide DNAs, we could regulate the hyperprocessing reaction by the bacterial RNase P enzymes. These techniques will lead the RNase P ribozyme to more designable and more applicable RNA-cleaving enzyme.

Bacteria↗

PubMed2002

Efficacy of plastic tube stents without side holes for middle and lower biliary strictures.

BACKGROUND: Although biliary expandable metallic stents (EMS) improve patency, they are unsuitable for primary biliary stenting. Although plastic tube stents without side holes (PWOS) are also reported to prolong patency, their efficacy remains controversial. GOALS: To evaluate clinical utility and relative advantages, we reviewed clinical results of three types of stents: plastic tube stents with side holes (PS), PWOS, and EMS. STUDY: The 130 patients comprised 56 with pancreatic cancers, 26 with gallbladder cancers, 21 with bile duct cancers, and 27 with other malignant diseases. Plastic tube stents with side holes (10 French [Fr]), PWOS (10 Fr), and EMS (30 Fr) were inserted in 64, 28, and 38 cases, respectively. RESULTS: Overall cumulative stent patency rates for EMS and PWOS groups were significantly higher than that of PS. This was also the case with middle and lower biliary tract strictures and with pancreas cancers. In Japan, medical costs with endoscopic retrograde cholangiopancreatography ($631.00) divided by the mean patent period with PS, PWOS, and EMS were $8.80/d, $4.60/d, and $20.40/d, respectively. CONCLUSION: We recommend PWOS for primary biliary stenting of middle and lower biliary strictures, especially those caused by pancreatic cancer, based on its lower price and sufficient patency without replacement after diagnosis of inoperability.

Adult↗

PubMed2002

Kinetics of hyperprocessing reaction of human tyrosine tRNA by ribonuclease P ribozyme from Escherichia coli.

Human tyrosine tRNA and fly alanine, histidine, and initiator methionine tRNAs are generally cleavable internally by bacterial ribonuclease P ribozyme. The unusual internal cleavage reaction of tRNA, called hyperprocessing, occurs when the cloverleaf structure of the tRNA molecule is denatured to form a double-hair-pin-like structure. The hyperprocessing reaction of these tRNAs requires magnesium ions. We analyzed details of this reaction using human tyrosine tRNA and Escherichia coli RNase P ribozyme. The usual processing reaction occurred efficiently with magnesium at 5 mM, but for the hyperprpocessing reaction, higher concentrations were needed. With such high concentrations, hyperprocessing cleaved both mature tRNA and tRNA precursor as substrates. When mature tRNA was the substrate, the apparent K(M) was almost the same as in the usual reaction, but k(cat) was smaller. These results indicated that the occurrence of hyperprocessing depends on the magnesium ion concentration, and suggested that magnesium ions contribute to the recognition of the shape of the substrate by bacterial RNase P enzymes.

Base Sequence↗