EXTENSIVE MATERNAL REPRESENTATION OF DNA-BINDING PROTEINS THAT INTERACT WITH REGULATORY TARGET SITES OF THE STRONGYLOCENTROTUS-PURPURATUS CYIIIA GENE

Nine different embryonic transcription factors interact at specific ta rget sites in the cis-regulatory domain of the Strongylocentrotus purp uratus CyIIIa ne. We tested eight of these site sequences and show her e that for every one a DNA-binding protein was present in unfertilized egg cytoplasm, The concentrations of active DNA-binding proteins per egg were estimated. We also present a new and convenient method for pr eparation of a maternal cytoplasmic fraction that retains these factor s in active form.