STUDY ON TRANSCRIPTION FACTORS REGULATING GENE EXPRESSION IN SEA URCHIN EMBRYOS

本研究旨在阐明海胆早期发育过程中与时间和空间调控基因表达相关的一系列转录因子。本研究期间取得的结果如下：(1)建立了用基因枪将外源DNA导入海胆卵的方法。(2)ars基因的时间表达受其启动子区域的两个不同的顺式元件(从-252到+38bp)的调控，尽管这些元件单独启动的转录水平很低且迅速下降。(3)ars基因第一内含子中的GGATTA序列(称为转录因子0tx的结合位点)是该基因的转录增强子。Hp0tx编码基因(Hp0tx_E和Hp0tx_L)已被克隆。Hp0tx_E是母性因子，抑制ars基因的转录，而Hp0tx_L是在孵化的囊胚中产生的，激活ars基因的转录。同一基因通过选择性剪接产生两个cDNA。(4)发现Ars基因-2686~-2113bp区域作为转录绝缘体，阻止Ars基因在邻近基因启动子的影响下转录。

The present research project has been undertaken to elucidate a cascade of transcription factors related to temporally and spatially regulated expression of genes during early development of sea urchin. Results obtained during the research period for this grant are as follows.(1) A procedure to introduce exogenous DNA into sea urchin eggs by a particle gun has been developed.(2) Temporal expression of the Ars gene is regulated by two distinct cisactive elements in its promoter region (from -252 to +38bp), though level of transcription initiated by these elements alone is very low and declines rapidly.(3) GGATTA sequences (known as binding sites for transcription factor 0tx) in the first intron of the Ars gene act as a transcriptional enhancer of this gene. Two distinct cDNAs (Hp0tx_E and Hp0tx_L) encoding Hp0tx have been cloned. Hp0tx_E is a maternal factor and suppresses the Ars gene transcription, while Hp0tx_L is produced in hatched blastulae and activates the Ars gene transcription. Two cDNAs are produced from the same gene by alternative splicing.(4) It is found that the region from -2686 to -2113bp of the Ars gene acts as an transcriptional insulator that prevents the Ars gene to be transcribed under the influence of promoter of the gene located in a closely vicinity.