Effects of cordycepin and cell dissociation on the synthesis of H1 histone by sea urchin embryos.

A shift in the type of H1 histone synthesized during sea urchin development has been described previously. Early histone synthesis appears to be carried out using both newly transcribed mRNA and stored maternal message. The appearance of the later H1 molecule is reported to be under transcriptional control. The present report utilizes hybrid embryos and supports the idea of transcriptional control of the later histone, from mesenchyme blastula on. In addition, the inhibition of the switch from one H1 type to the other by cordycepin is described and discussed. Since one effect of cordycepin is the dissociation of the blastula into single cells, the effect of other means of dissociation was studied. No interference with the histone changeover was detected in cultures of dissociated embryonic cells.