Temasek Life Sciences Laboratory, 1 Research Link National University of Singapore, Singapore 117604.
Development. 2012 Dec;139(24):4505-13. doi: 10.1242/dev.082867. Epub 2012 Nov 7.
In Drosophila, Maelstrom is a conserved component of the perinuclear nuage, a germline-unique structure that appears to serve as a site for Piwi-interacting RNA (piRNA) production to repress deleterious transposons. Maelstrom also functions in the nucleus as a transcriptional regulator to repress the expression of microRNA-7, a process that is essential for the proper differentiation of germline stem cells. In this paper, we report another function of Maelstrom in regulating oocyte determination independently of its transposon silencing and germline stem cell differentiation activities. In Drosophila, the conserved serine 138 residue in Maelstrom is required for its phosphorylation, an event that promotes oocyte determination. Phosphorylation of Maelstrom is required for the repression of the pachytene checkpoint protein Sir2, but not for transposon silencing or for germline stem cell differentiation. We identify Polo as a kinase that mediates the phosphorylation of Maelstrom. Our results suggest that the Polo-mediated phosphorylation of Maelstrom may be a mechanism that controls oocyte determination by inactivating the pachytene checkpoint via the repression of Sir2 in Drosophila ovaries.
在果蝇中，Maelstrom 是核周巢状结构的一个保守成分，该结构是生殖系特有的，似乎作为 Piwi 相互作用 RNA（piRNA）产生的位点，以抑制有害转座子。Maelstrom 还在核内作为转录调节剂发挥作用，抑制 microRNA-7 的表达，这一过程对于生殖干细胞的正常分化是必不可少的。在本文中，我们报道了 Maelstrom 的另一个功能，即独立于其转座子沉默和生殖干细胞分化活性来调节卵母细胞的决定。在果蝇中，Maelstrom 中的保守丝氨酸 138 残基需要磷酸化，这一事件促进卵母细胞的决定。Maelstrom 的磷酸化对于减数分裂前期检查点蛋白 Sir2 的抑制是必需的，但对于转座子沉默或生殖干细胞分化则不是必需的。我们确定 Polo 是一种激酶，可介导 Maelstrom 的磷酸化。我们的结果表明，Polo 介导的 Maelstrom 磷酸化可能是一种通过抑制果蝇卵巢中的 Sir2 来使减数分裂前期检查点失活从而控制卵母细胞决定的机制。
