Freeman R S, Kanki J P, Ballantyne S M, Pickham K M, Donoghue D J
Department of Chemistry, University of California at San Diego, La Jolla 92093.
J Cell Biol. 1990 Aug;111(2):533-41. doi: 10.1083/jcb.111.2.533.
Previous work has demonstrated that the Xenopus protooncogene mosxe can induce the maturation of prophase-arrested Xenopus oocytes. Recently, we showed that mosxe can transform murine NIH3T3 fibroblasts, although it exhibited only 1-2% of the transforming activity of the v-mos oncogene. In this study we have investigated the ability of the v-mos protein to substitute for the mosxe protein in stimulating Xenopus oocytes to complete meiosis. Microinjection of in vitro synthesized RNAs encoding either the mosxe or v-mos proteins stimulates resting oocytes to undergo germinal vesicle breakdown. Microinjection of an antisense oligonucleotide spanning the initiation codon of the mosxe gene blocked progesterone-induced oocyte maturation. When oocytes were microinjected first with the mosxe antisense oligonucleotide, and subsequently with in vitro synthesized v-mos RNA, meiotic maturation was rescued as evidenced by germinal vesicle breakdown. The v-mos protein exhibited in vitro kinase activity when recovered by immunoprecipitation from either microinjected Xenopus oocytes or transfected monkey COS-1 cells; however, in parallel experiments, we were unable to detect in vitro kinase activity associated with the mosxe protein. Microinjection of in vitro synthesized v-mos RNA into cleaving Xenopus embryos resulted in mitotic arrest, demonstrating that the v-mos protein can function like the mosxe protein as a component of cytostatic factor. These results exemplify the apparently conflicting effects of the v-mos protein, namely, its ability to induce maturation of oocytes, its ability to arrest mitotic cleavage of Xenopus embryo, and its ability to transform mammalian fibroblasts.
先前的研究表明，非洲爪蟾原癌基因mosxe能够诱导处于前期阻滞的非洲爪蟾卵母细胞成熟。最近，我们发现mosxe能够转化小鼠NIH3T3成纤维细胞，尽管它仅表现出v-mos癌基因转化活性的1-2%。在本研究中，我们探究了v-mos蛋白在刺激非洲爪蟾卵母细胞完成减数分裂方面替代mosxe蛋白的能力。显微注射体外合成的编码mosxe或v-mos蛋白的RNA可刺激静止的卵母细胞发生生发泡破裂。显微注射一段跨越mosxe基因起始密码子的反义寡核苷酸可阻断孕酮诱导的卵母细胞成熟。当先向卵母细胞显微注射mosxe反义寡核苷酸，随后再显微注射体外合成的v-mos RNA时，生发泡破裂证明减数分裂成熟得以挽救。当通过免疫沉淀从显微注射的非洲爪蟾卵母细胞或转染的猴COS-1细胞中回收时，v-mos蛋白表现出体外激酶活性；然而，在平行实验中，我们未能检测到与mosxe蛋白相关的体外激酶活性。向正在分裂的非洲爪蟾胚胎显微注射体外合成的v-mos RNA会导致有丝分裂停滞，这表明v-mos蛋白可作为细胞静止因子的一个组分发挥与mosxe蛋白类似的功能。这些结果例证了v-mos蛋白明显相互矛盾的作用，即其诱导卵母细胞成熟的能力、其阻止非洲爪蟾胚胎有丝分裂分裂的能力以及其转化哺乳动物成纤维细胞的能力。
