Cáceres Lucía, Nilson Laura A
Department of Biology, McGill University, QC, Canada.
Dev Biol. 2009 Feb 15;326(2):327-34. doi: 10.1016/j.ydbio.2008.11.030. Epub 2008 Dec 7.
Establishment of the Drosophila dorsal-ventral axis depends upon the correct localization of gurken mRNA and protein within the oocyte. gurken mRNA becomes localized to the presumptive dorsal anterior region of the oocyte, but is synthesized in the adjoining nurse cells. Normal gurken localization requires the heterogeneous nuclear ribonucleoprotein Squid, which binds to the gurken 3' untranslated region. However, whether Squid functions in the nurse cells or the oocyte is unknown. To address this question, we generated genetic mosaics in which half of the nurse cells attached to a given oocyte are unable to produce Squid. In these mosaics, gurken mRNA is localized normally but ectopically translated during the dorsal anterior localization process, even though the oocyte contains abundant Squid produced by the wild type nurse cells. These data indicate that translational repression of gurken mRNA requires Squid function in the nurse cells. We propose that Squid interacts with gurken mRNA in the nurse cell nuclei and, together with other factors, maintains gurken in a translationally silent state during its transport to the dorsal anterior region of the oocyte. This translational repression is not required for gurken mRNA localization, indicating that the information repressing translation is separable from that regulating localization.
果蝇背腹轴的建立取决于gurken mRNA和蛋白质在卵母细胞内的正确定位。gurken mRNA定位于卵母细胞的假定背前部区域，但在相邻的滋养细胞中合成。正常的gurken定位需要异质性核核糖核蛋白Squid，它与gurken的3'非翻译区结合。然而，Squid是在滋养细胞还是在卵母细胞中发挥作用尚不清楚。为了解决这个问题，我们构建了基因嵌合体，其中附着在给定卵母细胞上的一半滋养细胞无法产生Squid。在这些嵌合体中，gurken mRNA正常定位，但在背前部定位过程中发生异位翻译，尽管卵母细胞含有野生型滋养细胞产生的大量Squid。这些数据表明，gurken mRNA的翻译抑制需要Squid在滋养细胞中发挥作用。我们提出，Squid在滋养细胞核中与gurken mRNA相互作用，并与其他因子一起，在gurken mRNA运输到卵母细胞背前部区域的过程中使其保持翻译沉默状态。这种翻译抑制对于gurken mRNA的定位不是必需的，这表明抑制翻译的信息与调节定位的信息是可分离的。
