Yukio Sugino

Ansamitocin, a group of novel maytansinoid antibiotics with antitumour properties from Nocardia

WE have isolated a new group of ansamycin antibiotics with potent antitumour activity, from a fermentation broth of Nocardia sp. No. C-15003 (N-l) and have named it ansamitocin. Structures of ansamitocin were found to be similar to maytansine and related maytansinoids obtained from plant sources by Kupchan et al.1–4 and Wani et al.5. These comounds have strong antitumour activities, but development of production would be difficult, because plants containing maytansinoids are only harvested in tropical areas and their content in the plants is extremely low. Some attempts have been made to find a maytansinoid-producing microorganism6, but no success has been reported. We report here the microbial production, isolation and structural elucidation of these antibiotics and their antitumour activities against several experimental tumours in mice.

Cloning of rat brain protein kinase C complementary DNA

Four peptides derived from rat brain protein kinase C were partially sequenced. Using synthetic oligonucleotides deduced from the amino acid sequences as probes, a clone of complementary DNA (cDNA) was isolated from a cDNA library prepared from the same tissue. The nucleotide sequence of this cDNA clone revealed the primary structure of the carboxyl‐terminal region as having 224 amino acids, with significant sequence homology with cyclic AMP‐dependent and cyclic GMP‐dependent protein kinases.

Antitumor activity of carboxymethylglucans obtained by carboxymethylation of (1→3)-β-d-glucan from Alcaligenes faecalis var. myxogenes IFO 13140☆

Abstract Soluble carboxymethylglucans were obtained by carboxymethylation of insoluble ( 1→3 )-β- d -glucan from Alcaligenes faecalis var. myxogenes IFO 13140 . Carboxymethylglucan with DS 0.47 ( DS , number-average degree of carboxymethyl groups substituted per anhydroglucose unit) strongly inhibited growth of sarcoma 180 solid-type tumor when injected daily i.p. ( 3–40 mg/kg ) or i.v. ( 5 mg/kg ) for 10 days . It also strongly inhibited growth of Sarcoma 180 when injected i.p. in a single dose of 20–200 mg/kg 7 days after tumor transplantation. The DS of carboxymethylglucans was found to be closely correlated with their antitumor activity, compounds with a DS of about 1.0 per glucose residue having less activity. This chemically modified glucan seemed to have a host-mediated action, because it had no cytotoxic effect in vitro and because it was effective when injected before tumor transplantation.

Gelation of limulus amoebocyte lysate by an antitumor (1→3)-β-D-glucan

Abstract An antitumor carboxymethylated (1→3)-β-D-glucan (CMPS) was found to have a potent ability to cause gelation of the amoebocyte lysate of horseshoe crab at concentrations as low as 10−6 mg/ml. The gelation of the lysate and the activation of the proclotting enzyme in the lysate caused by CMPS were unique in that these reactions occurred at CMPS concentrations ranging from 10−6 to 10−3 mg/ml. The optimum concentration was 10−5 – 10−4 mg/ml and at concentrations above 10−2 mg/ml no gelation occurred. This gelation pattern was also observed in common with other antitumor polysaccharides. The mechanism of the gelation caused by CMPS was revealed to be distinctly different from that working in the gelation caused by endotoxins.

Ultraviolet inactivation of avian sarcoma viruses: biological and biochemical analysis.

Abstract The rate of inactivation by ultraviolet light of the focus-forming capacity of avian sarcoma virus was almost the same as that of the virus-producing capacity, measured as plaque formation. In addition, no significant difference was observed in inactivation of the transforming capacity assayed on C/BE chick embryo fibroblasts (CEF), which carry endogenous avian tumor virus DNA, and on duck embryo fibroblasts (DEF), which are known to be devoid of this DNA. All foci induced by nonirradiated virus produced infectious sarcoma virus, but some of the foci induced by uv-irradiated virus did not produce infectious virus of either transforming or transformation-defective type. The proportion of nonproducer foci was 3.4 times more in DEF than in gs− chf− CEF. RNAs extracted from uv-irradiated virions by sodium dodecyl sulfate (SDS) treatment were found to be composed of 60–70 S and 4 S RNAs by analysis in a sucrose gradient containing 0.5% SDS. The large RNA, however, became hydrophobic after irradiation and was sedimented with SDS by addition of one drop of saturated potassium chloride solution. This RNA was not dissociated into 30–40 S components by heating at 100° for 45 sec, unlike 60–70 S RNA from unirradiated virions. After SDS-Pronase treatment, the 60–70 S RNA from uv-irradiated virions no longer had these altered characteristics. Reverse transcriptase activity with the endogenous template decreased in parallel with increase in the uv dose. The reduction rate was similar to that assayed with exogenous template or in the presence of actinomycin D. These data strongly suggest that RNA damage is not the only cause of virus inactivation by uv light.

Studies on deoxynucleosidic compounds. II. Deoxycytidine diphosphate choline in sea urchin eggs.

Abstract 1. 1. A new deoxynucleotide derivative was found in sea urchin eggs and was identified as deoxy-CDP-choline. 2. 2. Deoxy-CPD-choline was synthesized chemically. 3. 3. In addition to deoxy-CDP-choline, a large amount of CDP-choline was found in sea urchin eggs. 4. 4. The structureal characteristics and biological significance of the “masked” deoxynucleosidic compounds including deoxy-CDP-choline have been discussed.

Studies on deoxynucleosidic compounds: I. A modified microbioassay method and its application to sea urchin eggs and several other materials☆

Abstract 1. 1. By modifying Hoff-Jorgensens microbiological assay method for deoxynucleosides, viz . by digesting samples to be assayed with a snake venom enzyme, it was possible to detect a new group of deoxynucleosidic compounds. This group of deoxynucleosidic compounds, differing from either simple deoxynucleosides or deoxynucleotides, were tentatively designated as “masked” deoxynucleosidic compounds. 2. 2. “Masked” deoxynucleosidic compounds were detected in various tissues such as sea urchin eggs and embryos and mammalian tissues including tumors. 3. 3. The relative amounts of “masked” deoxynucleosidic compounds compared with DNA or simple deoxynucleosidic compounds in eggs and early embryos were markedly higher than those in adult tissues. In this connection, the biological significance of “masked” deoxynucleosidic compounds was discussed.

Spontaneous Production of a C-Type RNA Virus in a Cell Line Derived from Rat Glioma

The spontaneous production of a rat C‐type RNA virus (ACV) in a cultured cell line (AC cells) established from a chemically induced rat glioma was studied. The characteristics of ACV were: morphology typical of C‐type RNA virus; buoyant density of 1.15 g/ml in a sucrose density gradient; RNA directed DNA polymerase activity; viral core with a density of 1.28 to 1.30 g/ml; 70S RNA with dimer structure; and structural protein composed of mainly four polypeptides. Kinetical analysis of DNA‐DNA hybridization revealed that DNA sequences homologous to DNA transcripts of RNA of ACV were present in rat cells. RNA directed DNA polymerase of ACV partially cross‐reacted with antiserum to the polymerase of Rauscher murine leukemia virus. These data suggest that ACV is an endogenous C‐type RNA virus of rat origin.