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Y Sokawa

Publications and source records attributed to Y Sokawa.

5 recordsLinked to original sources
PubMed1979

2',5'-Oligoadenylate synthetase activity in lymphocytes from normal mouse.

The activity of 2',5'-oligoadenylate synthetase, an enzyme recently discovered in interferon-treated cells, was found in lymphocytes from normal mouse spleen that had received neither exogenous interferon nor its inducers. The oligoadenylate synthesized by lymphocyte cell extracts inhibited protein synthesis in rabbit reticulocyte lysates. The oligomers were composed mainly of trimer and were resistant to digestion by T2 ribonuclease. The level of the enzyme in lymphocytes was about 20 to 30% of that in L929 cells treated with interferon. The activity of the enzyme was further enhanced in lymphocytes in vitro by addition of interferon. The 2',5'-oligoadenylate synthetase was distributed among several lymphoid tissues, but was not detected in cell extracts from brain or liver. The enzyme may play an important role in the regulation of the immune system.

Adenosine Monophosphate↗
PubMed1978

Relaxation effect of chloramphenicol on the stringent control in Escherichia coli.

In 10B601 (rel+) strain possessing a temperature-sensitive valyl-tRNA synthetase, chloramphenicol prevented the formation of guanosine-3'-diphosphate-5'-diphosphate (ppGpp) as well as the stringent control of stable RNA synthesis, under the conditions where the incorporation of valine into protein was still detectable i.e. at the lower restrictive temperatures. On the other hand, the effect of chloramphenicol was not observed at higher restrictive temperatures above 42 degrees C where the incorporation of valine was completely absent. Pretreatment of 10B601 cells with chloramphenicol before transfer to a high restrictive temperature (43.5 degrees C) did retard the onset of accumulation of ppGpp after the shift-up. Duration of the lag period was dependent on the concentration of chloramphenicol added. In parallel with the inability of the cells to accumulate ppGpp, stable RNA synthesis was permitted to continue at that high temperature. These results suggest that chloramphenicol traps aminoacyl-tRNA at the A-sites of ribosomes by damming-up the small flow of aminoacyl-tRNA under the restrictive supply of amino acids. Unchanged tRNA which has been located at the A-site is replaced by the charged one, thus resulting in the suppression of ppGpp formation and in the restoration of stable RNA synthesis.

Biological Transport↗
PubMed1978

Effect of interferon on the cell cycle of BALB/c 3T3 cells.

The effect of interferon on the exponential growth phase of BALB/c 3T3 cells was studied. Although interferon reduced the growth rate and the proportion of cells in both the M and S phases (mitotic index and labelling index), there were no appreciable differences in the duration of these phases between control and interferon-treated cells. Moreover, the shape of the first peak of the fraction of labelled mitoses (FLM) curve was not altered by treatment with interferon, which indicates that the duration of the S and G2 phases was not affected. However, the height of the second peak of the curve in interferon-treated cells was extremely reduced as compared to control culture. These results are compatible with the idea that the suppressive effect of interferon is exerted mainly in the G1 phase (A-state) of the cell cycle of BALB/c 3T3 cells.

Animals↗
PubMed1975

Regulation of stable RNA synthesis and ppGpp levels in growing cells of Escherichia coli.

Under the balanced condition of growth of E. coli cells, no distinct difference is observed in stable RNA and protein synthesis between CP78 (rel+) and CP79 (rel minus), whereas a considerable difference is present in RNA accumulation between NF161 (rel+) and NF162 (rel minus), where NF161 smaller than NF162. The RNA content of NF161 is lower than that of NF162 in four different cultures with different growth rates. These two sets of isogenic pairs of rel+ and rel minus strains are commonly used in the study of rel gene function; however, NF161 is a mutant in the spoT gene whose product may be responsible for the degradation of ppGpp. The basal levels of ppGpp in these four strains growing with three different growth rates were examined: NF161 (rel+ spoT minus) has a much higher content of ppGpp than do other strains. Furthermore, the contents of ppGpp tend to be lower when the above four strains are growing at a faster rate. Thus a close correlation seems to exist between the content of RNA and the basal level of ppGpp under the condition of balanced growth.

Adenosine Triphosphate↗