A study on the regulation of gene expression in sea urchin embryo.

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In order to get an insight into the mechanism regulating gene expression during early development, we have started our research on the mechanism regulating the transcription of arylsulfatase (Ars) gene in the sea urchin embryo. Results of the present study are summarized as follows.(1) In addition to the minimal promoter containing a TATA sequence, the 5' flanking region of the Ars gene contains several transcription enhancer sequences in between -3kbp and -1.9kbp, and a transcription silencer sequence in between -1.5kbp and -1.3kbp.(2) Many proteins that bind to enhancer and silencer regions were detected by gel band mobility shify assay, and the nucleotide sequences within these regions that were protected by these proteins were determined by footprinting. Since patterns of appearance of these proteins in nuclei changed depending on developmental stages, it was assumed that these proteins are transacting factors for the Ars gene transcription.(3) The silencer region is a CT-rich region with nearly 90% of the bases in this region occupied by cytosine or thymine. It was revealed by Sl nuclease assay that a (CT)_<11> tract in this region can take a triplex DNA configuration that is expected to be a recognizing site for specific trans-acting factors. It was found by south-western blotting that several nuclear proteins bind to the silencer region, and some of them appear and disappear depending on developmental stages. We have already started the isolation of these DNA binding proteins.