Okadaic acid mimics a nuclear component required for cyclin B-cdc2 kinase microinjection to drive starfish oocytes into M phase.
Okadaic acid mimics a nuclear component required for cyclin B-cdc2 kinase microinjection to drive starfish oocytes into M phase.
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DOI：
10.1083/jcb.115.2.337
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发表时间：
1991-10
期刊：
影响因子：
--
通讯作者：
Dorée M
中科院分区：
文献类型：
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作者：
Picard A;Labbé JC;Barakat H;Cavadore JC;Dorée M
G2期阻滞的卵母细胞含有cdc 2激酶作为一种无活性的细胞周期蛋白B-cdc 2复合物。当少量的高度纯化和活性的cdc 2激酶，制备从海星卵母细胞在第一次减数分裂中期，显微注射到非洲爪蟾卵母细胞，它诱导激活的非活性内源性复合物，因此，驱动受体卵母细胞进入M期。相比之下，在海星卵母细胞中，微注射的激酶经历快速失活，其保持在G2期被捕。内源性cdc 2激酶在有核和去核海星卵母细胞中被激活，在核膜破裂时用取自成熟卵母细胞的细胞质注射，但只有取自有核卵母细胞的细胞质此后才能从G2停滞释放第二受体卵母细胞，因此含有M期促进因子（MPF）活性。当冈田酸阻断2A型磷酸酶时，有核和去核海星卵母细胞都产生MPF活性。如果2A型磷酸酶仅被部分抑制，则有核卵母细胞和去核卵母细胞都不产生MPF活性，尽管如果随后注射纯化的cdc 2激酶作为引物以激活内源性激酶，则两者都产生MPF活性。海星卵母细胞的细胞核含有2A型磷酸酶抑制剂，但既不活跃也不不活跃的cdc 2激酶。将细胞核内的物质注射到G2期阻滞的海星卵母细胞的细胞质中，激活内源性cdc 2激酶，产生MPF活性，并驱动受体卵母细胞进入M期。总之，这些结果表明，MPF放大环的控制，积极和消极的，cdc 2激酶和2A型磷酸酶，分别。海星MPF扩增环的激活需要核组分来抑制细胞质中的2A型磷酸酶。
G2-arrested oocytes contain cdc2 kinase as an inactive cyclin B-cdc2 complex. When a small amount of highly purified and active cdc2 kinase, prepared from starfish oocytes at first meiotic metaphase, is microinjected into Xenopus oocytes, it induces activation of the inactive endogenous complex and, as a consequence, drives the recipient oocytes into M phase. In contrast, the microinjected kinase undergoes rapid inactivation in starfish oocytes, which remain arrested at G2. Endogenous cdc2 kinase becomes activated in both nucleated and enucleated starfish oocytes injected with cytoplasm taken from maturing oocytes at the time of nuclear envelope breakdown, but only cytoplasm taken from nucleated oocytes becomes able thereafter to release second recipient oocytes from G2 arrest, and thus contains M phase-promoting factor (MPF) activity. Both nucleated and enucleated starfish oocytes produce MPF activity when type 2A phosphatase is blocked by okadaic acid. If type 2A phosphatase is only partially inhibited, neither nucleated nor enucleated oocytes produce MPF activity, although both do so if purified cdc2 kinase is subsequently injected as a primer to activate the endogenous kinase. The nucleus of starfish oocytes contains an inhibitor of type 2A phosphatase, but neither active nor inactive cdc2 kinase. Microinjection of the content of a nucleus into the cytoplasm of G2-arrested starfish oocytes activates endogenous cdc2 kinase, produces MPF activity, and drives the recipient oocytes into M phase. Together, these results show that the MPF amplification loop is controlled, both positively and negatively, by cdc2 kinase and type 2A phosphatase, respectively. Activation of the MPF amplification loop in starfish requires a nuclear component to inhibit type 2A phosphatase in cytoplasm.