Patterns and rates of protein synthesis in sea urchin embryos: I. Uptake and incorporation of amino acids during the first cleavage cycle

Abstract

Uptake and incorporation of amino acids during the first cleavage of developing sea urchins decreased at about the time of metaphase. The pattern of apparent rate changes is not coupled to karyokinesis or to cytokinesis. It appears not to represent a fluctuation in the true rate of protein synthesis, but only a transient variation in permeability during the cell cycle. The metaphase depression in uptake and incorporation observed in sea urchin embryos is thus quite different from the metaphase arrest of protein synthesis in HeLa cells. Control of translation by factors released from nuclei at metaphase (as has been proposed for the cells in culture) thus does not operate in the cleaving embryos.