Nuclear envelope precursor vesicle targeting to chromatin is stimulated by protein phosphatase 1 in Xenopus egg extracts
Nuclear envelope precursor vesicle targeting to chromatin is stimulated by protein phosphatase 1 in Xenopus egg extracts
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DOI：
10.1016/j.yexcr.2007.03.015
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发表时间：
2007-05-15
影响因子：
3.7
通讯作者：
Horigome, Tsuneyoshi
中科院分区：
文献类型：
--
作者：
Ito, Hiromi;Koyama, Yuhei;Horigome, Tsuneyoshi
利用体外无细胞系统研究了有丝分裂结束时核膜靶向染色质的机制，该系统包括非洲爪哇卵膜和胞浆部分以及精子染色质。有丝分裂相膜是从非洲爪蛙卵的有丝分裂期提取液中分离出来的，不能与染色质结合，但在用非洲爪哇卵胞浆合成部分进行预处理后，能够与染色质结合。当胞浆中的蛋白磷酸酶1(PP1)被抗非洲爪蛙PP1-Gamma 1抗体清除时，这种能力就丧失了。将重组的xPP1-γ1加入到PP1耗尽的胞质组分中，恢复了这种能力。这些和其他结果表明，在合成阶段，PP1使膜上有丝分裂的磷酸化位点去磷酸化，促进了膜对染色质的靶向。另一方面，含有层蛋白B受体(LBR)染色质结合域但不含Emerin的片段抑制了膜小泡的靶向。研究还表明，PP1使一个负责调节LBR与染色质结合的磷酸基团(S)去磷酸化。讨论了PP1和LBR参与核膜靶向染色质调控的可能机制。(C)2007 Elsevier Inc.保留所有权利。
The mechanism underlying targeting of the nuclear membrane to chromatin at the end of mitosis was studied using an in vitro cell-free system comprising Xenopus egg membrane and cytosol fractions, and sperm chromatin. The mitotic phase membrane, which was separated from a mitotic phase extract of Xenopus eggs and could not bind to chromatin, became able to bind to chromatin on pretreatment with a synthetic phase cytosol fraction of Xenopus eggs. When the cytosol fraction was depleted of protein phosphatase 1 (PP1) with anti-Xenopus PP1-gamma 1 antibodies, this ability was lost. The addition of recombinant xPP1 gamma 1 to the PP1-depleted cytosol fraction restored the ability. These and other results suggested that dephosphorylation of mitotic phosphorylation sites on membranes by PP1 in the synthetic phase cytosol fraction promoted targeting of the membranes to chromatin. On the other hand, a fragment containing the chromatin-binding domain of lamin B receptor (LBR) but not emerin inhibited targeting of membrane vesicles. It was also shown that PP1 dephosphorylates a phosphate group(s) responsible for regulation of the binding of LBR to chromatin. A possible mechanism involving PP1 and LBR for the regulation of nuclear membrane targeting to chromatin was discussed. (c) 2007 Elsevier Inc. All rights reserved.