Nuclear import of the Drosophila Rel protein Dorsal is regulated by phosphorylation
Nuclear import of the Drosophila Rel protein Dorsal is regulated by phosphorylation
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DOI：
10.1101/gad.13.5.556
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发表时间：
1999-03-01
影响因子：
10.5
通讯作者：
Steward, R
中科院分区：
文献类型：
--
作者：
Drier, EA;Huang, LH;Steward, R
在果蝇中，背腹极性是由母体编码的信号转导途径决定的，该途径最终导致Rel蛋白Dorsal的分级核定位。Dorsal被I kappa B蛋白（Cactus）保留在细胞质中。Cactus的信号依赖性磷酸化导致Cactus的降解和Dorsal的核靶向。我们提出了一个深入的研究背磷酸化的功能重要性。我们发现，背侧磷酸化的腹侧信号，而与仙人掌，背侧磷酸化是必不可少的，其核输入。在Dorsal的磷酸化标记仅限于卵巢和早期胚胎中的丝氨酸残基中，在六个保守丝氨酸中具有突变的蛋白质废除Dorsal活性，是组成性细胞质，并且似乎消除Dorsal磷酸化，但仍然与仙人掌相互作用。两个单独的丝氨酸到丙氨酸突变产生意想不到的结果。在野生型信号背景下，高度保守的PKA位点（S312）的突变仅产生弱的功能丧失;然而，它在仙人掌突变体背景下完全使蛋白质不稳定。值得注意的是，另一个完全保守的丝氨酸（S317）的磷酸化调节在腹侧细胞中发现的高水平的核输入。我们的结论是，野生型背核梯度的形成需要仙人掌和背的磷酸化。丝氨酸的强保守性表明其他Rel蛋白的磷酸化对于它们的适当核靶向是必不可少的。
In Drosophila, dorsal-ventral polarity is determined by a maternally encoded signal transduction pathway that culminates in the graded nuclear localization of the Rel protein, Dorsal. Dorsal is retained in the cytoplasm by the I kappa B protein, Cactus. Signal-dependent phosphorylation of Cactus results in the degradation of Cactus and the nuclear targeting of Dorsal. We present an in-depth study of the functional importance of Dorsal phosphorylation. We find that Dorsal is phosphorylated by the ventral signal while associated with Cactus, and that Dorsal phosphorylation is essential for its nuclear import. In who phospholabeling of Dorsal is Limited to serine residues in both ovaries and early embryos, A protein bearing mutations in six conserved serines abolishes Dorsal activity, is constitutively cytoplasmic, and appears to eliminate Dorsal phosphorylation, but still interacts with Cactus. Two individual serine-to-alanine mutations produce unexpected results. In a wild-type signaling background, a mutation in the highly conserved PKA site (S312) produces only a weak loss-of-function; however, it completely destabilizes the protein in a cactus mutant background. Significantly, the phosphorylation of another completely conserved serine (S317) regulates the high level of nuclear import found in ventral cells. We conclude that the formation of a wild-type Dorsal nuclear gradient requires the phosphorylation of both Cactus and Dorsal. The strong conservation of the serines suggests that phosphorylation of other Rel proteins is essential for their proper nuclear targeting.