Biomedical subjects

Shigenobu Toné

Publications and source records attributed to Shigenobu Toné.

3 recordsLinked to original sources

PubMed2003

Induction of apoptosis by depletion of DNA topoisomerase IIalpha in mammalian cells.

Inactivation of topoisomerase (topo) IIalpha arrests murine embryonic development. In topo IIalpha-depleted embryos, nuclei were partitioned to daughter cells without complete separation and formed an interconnecting droplet-like structure. The present study examined the fates of topo IIalpha-depleted cells with the droplet-like nuclear structure. When the embryos with abnormal nuclei were further incubated, apoptosis was induced along with the formation of fragmented and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling positive nuclei. ICRF-193 treatment of embryos activated caspases. Apoptosis induced by ICRF-193 was suppressed by z-VAD-fmk, a caspase inhibitor, and pifithrin-alpha, a p53 inhibitor. Moreover, when mitosis was blocked by nocodazole, ICRF-193-induced nuclear abnormalities and apoptosis were abolished. These data suggest that cycling through the M-phase is essential for ICRF-193-induced apoptosis. Nuclear abnormalities similar to those of topo IIalpha-depleted embryos were induced in HeLa cells in which topo IIalpha was knocked down by transfection with short interfering RNA (siRNA) against topo IIalpha, followed by induction of apoptosis. Our results suggest that topo IIalpha-depleted cells with the droplet-like nuclear structure induce apoptosis, which is dependent on caspase and p53 activity during the G1 phase in mammalian cells.

Animals↗

PubMed2002

Functional analysis of the 5'-flanking region of the human alanine:glyoxylate aminotransferase gene AGXT.

Primer extension of human liver poly(A)(+) RNA revealed that the main transcription start site of the human alanine:glyoxylate aminotransferase gene (AGXT) is situated near 45 bp upstream from the translation start site. Deletion analysis using the 1203 bp 5'-flanking region of the AGXT gene and a luciferase reporter suggested that the promoter sequence is most likely located 2-325 bp upstream from the translation start site, possibly with enhancer elements 440-700 bp upstream. It was also suggested that the region -2 to -64 is important for the expression of the AGXT gene. The region -2 to -325 has two TATA boxes and some initiator elements.

Base Sequence↗

PubMed2002

A possible intermediate step during apoptotic execution.

Many proteases are known to be involved in apoptosis. Among them, interleukin-1beta converting enzyme (ICE) and its family proteases, which are called caspases, play critical roles in the execution stage of apoptosis. We previously reported that a proteasome-inhibitor, benzyloxycarbonyl Leu-Leu-leucinal (ZLLLal), induced apoptosis in MOLT-4 cells. In the present study, in order to analyze the detailed mechanism of ZLLLal-induced apoptosis, we examined the effect of a caspase-inhibitor, acetyl(Ac)-Tyr-Val-Ala-Asp-chloromethyl ketone (AcYVADcmk), on ZLLLal-induced apoptosis in the cells. Agarose gel electrophoresis revealed that low concentrations of AcYVADcmk efficiently suppressed apoptotic DNA fragmentation. However, the cells presented morphology different from normal, apoptotic or necrotic cells, although DNA fragmentation was suppressed. The same examination was performed on the cells with anti-Fas antibody-induced apoptosis, and the same results were obtained. Some cells with a similar morphology were found even without the caspase-inhibitor in the early stage of anti-Fas antibody-induced physiological apoptosis. In addition, apoptotic cascade was reactivated by washing out the caspase inhibitor from the DNA degradation-suppressed cells. Therefore, this newly found morphological feature shows the presence of a step prior to caspase activation in the cells, and this is the first report presenting the pre-caspase-activated step in the apoptotic cascade.

Amino Acid Chloromethyl Ketones↗