Synthesis of protein for DNA replication and cleavage events in the sand dollar embryo

Abstract

Cycloheximide, 1 μg/ml, inhibited protein synthesis in embryos of the sand dollar ( Echinarachnius parma), by 97%, but did not prevent extensive synthesis of DNA during S1. All subsequent DNA synthesis, however, was profoundly inhibited and cleavage did not occur. Embryos were exposed to the drug at progressively later intervals and their capacity for karyo- and cytokinesis, and for DNA synthesis was examined. Evidence was thereby obtained that proteins probably involved in subsequent synthesis of DNA, karyokinesis and cytocleavage were made intermittently for the purposes listed in that order, concurrent with the S-period itself or slightly thereafter. DNA was still synthesized on newly introduced sperm in animals rendered incapable of replicating their nuclear DNA by drug treatment. Thus, the drug-induced defect appears to involve the DNA itself rather than the availability of precursors or their polymerization on a suitable template.