Tomoko Tsuji

Purification and characterization of Erythroid Differentiation Factor(EDF) isolated from human leukemia cell line THP-1

We isolated a protein, from a cell line of human origin, which exhibits extensive differentiation inducing activity toward Friend leukemia cells. The protein, called Erythroid Differentiation Factor (EDF), was found in a 4 day culture of THP-1 cells performed in the presence of 4 beta-phorbol 12-myristate 13-acetate(PMA). EDF is a homodimer of a molecular weight of 25,000, with an NH2-terminal sequence identical to that of the beta A-chain of porcine Inhibin. It was suggested that a single protein species is responsible for the activities of both EDF and FRP, a FSH releasing protein isolated from porcine ovarian follicular fluid.

Development of Fertilized Starfish Eggs in Which Cytokinesis is Prevented by Iturin A–2

Iturin A–2, a cyclic peptide obtained from cultures of Bacillus subtilis inhibited cell division but not nuclear divisions of fertilized eggs of the starfish Asterina pectinifera, resulting in the formation of non‐cleaving eggs containing all the embryonic nuclei in a common cytoplasm. Fertilized eggs in which cleavage was prevented by iturin A–2 (50μg/ml) synthesized DNA, RNA and protein at comparable rates to those of normal embryos up to the onset of blastulation. In single‐cell embryos, however, elevation of the level of transcription, which is a characteristic marker of blastulation, did not take place and the chromatin masses eventually dispersed in the cytoplasm.

Isolation of iturin A-2 as an inhibitor of cytokinesis of starfish embryos

Abstract 1. 1. We have purified substances from the bacterium Bacillus subtilis that inhibit the cell division of embryos of the starfish, Asterina pectinifera , and which are identified as iturin A-2 and closely related cyclic peptides. 2. 2. Iturin A-2 at a concentration of 12.5 μg/ml or greater inhibited cell division of the fertilized starfish egg but not nuclear division, resulting in formation of a multinueleated unicellular embryo. 3. 3. Iturin A-2 microinjected into a fertilized egg was ineffective in halting cell division. 4. 4. From the results of these experiments, we conclude that the arrest of cleavage produced by iturin A-2 is due to the inability of the cell membrane to make a furrow at cytokinesis.