DEVELOPMENTAL UTILIZATION OF SPP3A1 AND SPP3A2 - 2 PROTEINS WHICH RECOGNIZE THE SAME DNA TARGET SITE IN SEVERAL SEA-URCHIN GENE REGULATORY REGIONS

SpP3A1 and SpP3A2 are DNA-binding proteins that interact specifically with the same target sites in the regulatory domains of the Strongyloc entrotus purpuratus CyIIIa gene and also of several other known genes. In this work we used antibodies raised against recombinant P3A1 and P 3A2 to quantitate these transcription factors in eggs and in the nucle ar compartments of embryos of various stages. Both proteins are presen t in unfertilized eggs, and both enter the embryonic nuclei early in d evelopment, but only P3A2 remains present in nuclei at functional conc entrations beyond the early gastrula stage. Combined with earlier meas urements of P3A site binding at cleavage stages, these measurements sh ow that P3A1 would be replaced by P3A2 at target sites in genes regula ted by these factors. (C) 1995 Aeademic Press, Inc.