PROTEIN-DNA INTERACTIONS AT PUTATIVE REGULATORY REGIONS OF 2 COORDINATELY EXPRESSED GENES, MSP130 AND PM27, DURING SKELETOGENESIS IN SEA-URCHIN EMBRYOS

Development of the primary mesenchyme cells (PMCs) of the sea urchin embryo, which give rise to the larval skeleton, involves the coordinate onset of expression of several structural genes. As part of an effort to identify cis-acting elements that might play a role in this regulatory event, co-regulated genes were examined by two approaches. First, they were compared for conserved sequence elements. Four conserved elements were found as a cluster in all three genes examined, suggesting a regulatory role. Second, as a test for potential function, the putative regulatory regions of two of these genes were examined for protein binding sites. DNase I protection and gel mobility shift assays were used to: 1) identify several nuclear protein binding sites in these regions, two of which correspond to conserved elements among the genes; 2) demonstrate that the developmental time of appearance of the proteins that interact with these sites corresponds to the time of activation of the genes; and 3) show that two of the conserved sequence elements shared by these genes compete for the same binding proteins. These data identify putative regulatory elements, whose specific roles in the coordinate regulation of PMC-expressed genes can now be addressed directly using appropriate transgenic expression constructs.