Wei Z, Angerer L M, Angerer R C
Department of Biology, University of Rochester, New York 14627, USA.
Dev Biol. 1997 Jul 1;187(1):71-8. doi: 10.1006/dbio.1997.8603.
The mechanism that establishes the maternally determined animal-vegetal axis of sea urchin embryos is unknown. We have analyzed the cis-regulatory elements of the SpHE gene of Strongylocentrotus purpuratus, which is asymmetrically expressed along this axis, in an effort to identify components of maternal positional information. Previously, we defined a regulatory region that is sufficient to provide correct nonvegetal expression of a beta-galactosidase reporter gene (Wei, Z., Angerer, L. M., Gagnon, M. L., and Angerer, R. C., Dev. Biol. 171, 195-211, 1995). We have now analyzed this region intensively in order to determine if the spatial pattern is controlled by nonvegetal-positive activities or by vegetal-negative activities. The regulatory sequences, except the basal promoter, were mutated by either deletion or sequence replacement. None of these mutations resulted in ectopic beta-gal expression in vegetal cells, showing that no single negative cis element is responsible for the lack of vegetal SpHE transcription. Surprisingly, even short segments of the regulatory region containing only several identified cis elements also direct nonvegetal expression. Furthermore, the SpHE basal promoter functions effectively in vegetal cells in combination with cis-acting elements derived from the PMC-specific gene, SM50. We conclude that the spatial pattern of SpHE transcription is achieved by multiple positive activities concentrated in nonvegetal cells. The vegetal expression of SM50 also is regulated only by positive activities (Makabe, K. W., Kirchhamer, C. V., Britten, R. J., and Davidson, E. H., Development 121, 1957-1970, 1995). A chimeric promoter containing both SpHE and SM50 regulatory sequences is active ubiquitously, suggesting that these regulators are not reciprocally repressive. These observations suggest a model in which the SpHE and SM50 genes are activated by separate sets of positive maternal activities concentrated, respectively, in nonvegetal and vegetal domains of the early embryo.
建立海胆胚胎母源性决定的动物 - 植物轴的机制尚不清楚。我们分析了紫海胆SpHE基因的顺式调控元件，该基因沿此轴不对称表达，旨在识别母源位置信息的组成部分。此前，我们定义了一个调控区域，该区域足以使β - 半乳糖苷酶报告基因实现正确的非植物性表达（Wei, Z., Angerer, L. M., Gagnon, M. L., and Angerer, R. C., Dev. Biol. 171, 195 - 211, 1995）。我们现在对该区域进行了深入分析，以确定其空间模式是由非植物性阳性活性还是由植物性阴性活性控制。除基础启动子外，调控序列通过缺失或序列替换进行了突变。这些突变均未导致植物细胞中异位β - 半乳糖苷酶表达，表明没有单一的负性顺式元件导致植物性SpHE转录缺失。令人惊讶的是，即使是仅包含几个已识别顺式元件的调控区域短片段也能指导非植物性表达。此外，SpHE基础启动子与源自中胚层特异性基因SM50的顺式作用元件结合后，在植物细胞中能有效发挥作用。我们得出结论，SpHE转录的空间模式是通过集中在非植物细胞中的多种阳性活性实现的。SM50的植物性表达也仅受阳性活性调控（Makabe, K. W., Kirchhamer, C. V., Britten, R. J., and Davidson, E. H., Development 121, 1957 - 1970, 1995）。一个包含SpHE和SM50调控序列的嵌合启动子在各处均有活性，这表明这些调节因子并非相互抑制。这些观察结果提示了一个模型，其中SpHE和SM50基因分别由集中在早期胚胎非植物性和植物性区域的不同组母源阳性活性激活。
