Jessus C, Rime H, Ozon R
Laboratoire de Physiologie de la Reproduction, Inra/CNRS ESA 7080, Université Pierre-et-Marie-Curie, Paris, France.
Biol Cell. 1998 Nov;90(8):573-83.
Oogonia undergo numerous mitotic cell cycles before completing the last DNA replication and entering the meiotic prophase I. After chromosome pairing and chromatid exchanges between paired chromosomes, the oocyte I remains arrested at the diplotene stage of the first meiotic prophase. Oocyte growth then occurs independently of cell division; indeed, during this growth period, oocytes (4n DNA) are prevented from completing the meiotic divisions. How is the prophase arrest regulated? One of the players of the prophase block is the high level of intracellular cAMP, maintained by an active adenylate cyclase. By using lethal toxin from Clostridium sordellii (LT), a glucosyltransferase that glucosylates and inactivates small G proteins of the Ras subfamily, we have shown that inhibition of either Ras or Rap or both proteins is sufficient to release the prophase block of Xenopus oocytes in a cAMP-dependent manner. The implications of Ras family proteins as new players involved in the prophase arrest of Xenopus oocytes will be discussed here.
卵原细胞在完成最后一次DNA复制并进入减数第一次分裂前期之前会经历多次有丝分裂细胞周期。在染色体配对以及配对染色体之间发生染色单体交换之后，卵母细胞I会停留在第一次减数分裂前期的双线期。然后，卵母细胞的生长独立于细胞分裂进行；实际上，在这个生长阶段，卵母细胞（4n DNA）被阻止完成减数分裂。前期阻滞是如何调节的呢？前期阻滞的参与者之一是由活性腺苷酸环化酶维持的高水平细胞内cAMP。通过使用来自索氏梭菌的致死毒素（LT），一种使Ras亚家族的小G蛋白糖基化并使其失活的葡糖基转移酶，我们已经表明，抑制Ras或Rap或这两种蛋白足以以cAMP依赖的方式解除非洲爪蟾卵母细胞的前期阻滞。本文将讨论Ras家族蛋白作为参与非洲爪蟾卵母细胞前期阻滞的新参与者的意义。
