A TISSUE-SPECIFIC REPRESSOR IN THE SEA-URCHIN EMBRYO OF LYTECHINUS-PICTUS BINDS THE DISTAL G-STRING ELEMENT IN THE LPS1-BETA PROMOTER

LpS1 RNA transcripts and proteins are expressed exclusively in the abo ral ectoderm of the embryo in the sea urchin Lytechinus pictus. We hav e characterized the LpS1-beta promoter to identify the cis-acting elem ents that may be involved in the aboral ectoderm-specific expression o f the LpS1-beta gene. The distal G-string site, composed of six contig uous guanine deoxynucleotides located at -721 to -726, was analyzed. A mutation at the distal G-string caused over a two-fold increase in re porter chloramphenicol acetyltransferase gene activity and inappropria te expression of reporter green fluorescent protein in nonaboral ectod erm cells in L. pictus embryos. These results suggest that the protein s that bind the distal G-string act as a spatial repressor in the nona boral ectoderm cells of the developing embryo.