Cell cycle dynamics of an M-phase-specific cytoplasmic factor in Xenopus laevis oocytes and eggs.
Cell cycle dynamics of an M-phase-specific cytoplasmic factor in Xenopus laevis oocytes and eggs.
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DOI：
10.1083/jcb.98.4.1247
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发表时间：
1984-04
期刊：
影响因子：
--
通讯作者：
Kirschner M
中科院分区：
文献类型：
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作者：
Gerhart J;Wu M;Kirschner M
我们研究了成熟促进因子(MPF)在非洲爪哇卵和卵母细胞有丝分裂和减数分裂细胞周期中的活性调节。为此，我们开发了一种小规模提取卵和卵母细胞的方法，并用稀释终点法测定了提取液中MPF的活性。我们发现，在卵母细胞中，MPF活性在生发泡破裂之前出现，然后在第一次减数分裂周期结束时迅速消失。在第二次减数分裂周期中，MPF在第二次中期之前重新出现，此时成熟停止。因此，MPF循环与减数分裂的缩短周期相一致。当低水平注射MPF诱导卵母细胞成熟时，放线菌酮不能阻止第一周期高水平MPF的出现。这种扩增表明MPF前体存在于卵母细胞中，并由翻译后方式激活，由低水平注射的MPF触发。此外，MPF在这类卵母细胞中几乎按时消失，表明MPF失活剂也通过翻译后方式激活。然而，在没有蛋白质合成的情况下，MPF永远不会出现在第二次减数分裂周期中。当受精或人工激活正常卵子时，MPF在8分钟内从细胞质中消失。在之后的一段时间内，灭活剂仍然能够摧毁注入鸡蛋中的大量MPF。当内源性MPF出现在第一个有丝分裂周期的前期时，它就失去活性。MPF和灭活剂在卵裂阶段的反复相互循环不受秋水仙素和诺可达唑的影响，因此不需要有效地完成纺锤体的形成、有丝分裂或胞质分裂。然而，MPF的出现被有丝分裂前应用的放线菌亚胺阻断，MPF的消失被细胞抑制因子阻止。在所有这些方面，MPF和灭活剂似乎与先前描述的非洲爪哇卵裂的细胞周期振荡器紧密相连，并可能参与其中(Hara，K.，P.Tydeman，和M.Kirschner，1980，proc。娜塔莉。阿卡德。SCI。美国，77：462-466)。
We have examined the regulation of maturation-promoting factor (MPF) activity in the mitotic and meiotic cell cycles of Xenopus laevis eggs and oocytes. To this end, we developed a method for the small scale extraction of eggs and oocytes and measured MPF activity in extracts by a dilution end point assay. We find that in oocytes, MPF activity appears before germinal vesicle breakdown and then disappears rapidly at the end of the first meiotic cycle. In the second meiotic cycle, MPF reappears before second metaphase, when maturation arrests. Thus, MPF cycling coincides with the abbreviated cycles of meiosis. When oocytes are induced to mature by low levels of injected MPF, cycloheximide does not prevent the appearance of MPF at high levels in the first cycle. This amplification indicates that an MPF precursor is present in the oocyte and activated by posttranslational means, triggered by the low level of injected MPF. Furthermore, MPF disappears approximately on time in such oocytes, indicating that the agent for MPF inactivation is also activated by posttranslational means. However, in the absence of protein synthesis, MPF never reappears in the second meiotic cycle. Upon fertilization or artificial activation of normal eggs, MPF disappears from the cytoplasm within 8 min. For a period thereafter, the inactivating agent remains able to destroy large amounts of MPF injected into the egg. It loses activity just as endogenous MPF appears at prophase of the first mitotic cycle. The repeated reciprocal cycling of MPF and the inactivating agent during cleavage stages is unaffected by colchicine and nocodazole and therefore does not require the effective completion of spindle formation, mitosis, or cytokinesis. However, MPF appearance is blocked by cycloheximide applied before mitosis; and MPF disappearance is blocked by cytostatic factor. In all these respects, MPF and the inactivating agent seem to be tightly linked to, and perhaps participate in, the cell cycle oscillator previously described for cleaving eggs of Xenopus laevis (Hara, K., P. Tydeman, and M. Kirschner, 1980, Proc. Natl. Acad. Sci. USA, 77:462- 466).