The effects of puromycin on mitotis, protein synthesis and DNA synthesis during cleavage of the amphibian egg

A study has been made of the effects of puromycin injected into Pleurodeles eggs. Cleavage of the eggs is rapidly blocked by this substance, after only a few mitoses.

Autoradiography using radioactive precursors (leucine, thymidine) has revealed that puromycin has no effect on protein and DNA synthesis during the first 3 hr. following injection. Cytoplasmic protein synthesis is interrupted at the end of this delay during the interphase of the 64-blastomere stage. Occasionally this final division occurs, but even then the inhibition of protein synthesis prevents the formation of the mitotic apparatus and the reduplication of DNA. Mitotic inhibition follows, usually at the 128-blastomere stage. It may thus be concluded that the inhibition of protein synthesis in the cytoplasm precedes the blocking of DNA synthesis and nuclear protein synthesis.

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