Rushlow C A, Han K, Manley J L, Levine M
Department of Biological Sciences, Fairchild Center, Columbia University, New York, New York 10027.
Cell. 1989 Dec 22;59(6):1165-77. doi: 10.1016/0092-8674(89)90772-1.
The maternal morphogen dorsal (dl) plays a key role in the establishment of dorsal-ventral polarity in Drosophila. We present evidence that the graded distribution of dl protein is initiated by selective nuclear transport. The dl protein is uniformly distributed throughout the cytoplasm of early embryos, but approximately 90 min after fertilization, dl protein present in ventral but not dorsal regions is selectively transported to the nucleus. Mutations in maternally active genes that regulate dl disrupt this transport process, resulting in an inactive, cytoplasmically localized form of the dl protein. Selective nuclear transport of dl protein was reproduced in tissue culture cells. The wild-type dl protein is largely restricted to the cytoplasm, while truncated proteins are predominantly localized within the nucleus. Transient cotransfection assays suggest that dl activates expression from several promoters in an apparently sequence-independent manner. We discuss the role of nuclear transport as a regulated process in gene expression and development.
母体形态发生素背腹因子（dl）在果蝇背腹极性的建立中起关键作用。我们提供的证据表明，dl蛋白的梯度分布是由选择性核转运启动的。dl蛋白在早期胚胎的整个细胞质中均匀分布，但在受精后约90分钟，腹侧而非背侧区域存在的dl蛋白被选择性地转运到细胞核。调控dl的母体活性基因突变会破坏这一转运过程，导致dl蛋白形成无活性的、定位于细胞质的形式。dl蛋白的选择性核转运在组织培养细胞中得以重现。野生型dl蛋白主要局限于细胞质，而截短的蛋白则主要定位于细胞核内。瞬时共转染实验表明，dl以一种明显不依赖序列的方式激活多个启动子的表达。我们讨论了核转运作为基因表达和发育中一个受调控过程的作用。
