Mayer Alexandra, Baran Vladimir, Sakakibara Yogo, Brzakova Adela, Ferencova Ivana, Motlik Jan, Kitajima Tomoya S, Schultz Richard M, Solc Petr
a Institute of Animal Physiology and Genetics AS CR , Libechov , Czech Republic.
b Institute of Animal Physiology , Kosice , Slovakia.
Cell Cycle. 2016;15(4):546-58. doi: 10.1080/15384101.2015.1128592. Epub 2016 Jan 8.
Because low levels of DNA double strand breaks (DSBs) appear not to activate the ATM-mediated prophase I checkpoint in full-grown oocytes, there may exist mechanisms to protect chromosome integrity during meiotic maturation. Using live imaging we demonstrate that low levels of DSBs induced by the radiomimetic drug Neocarzinostatin (NCS) increase the incidence of chromosome fragments and lagging chromosomes but do not lead to APC/C activation and anaphase onset delay. The number of DSBs, represented by γH2AX foci, significantly decreases between prophase I and metaphase II in both control and NCS-treated oocytes. Transient treatment with NCS increases >2-fold the number of DSBs in prophase I oocytes, but less than 30% of these oocytes enter anaphase with segregation errors. MRE11, but not ATM, is essential to detect DSBs in prophase I and is involved in H2AX phosphorylation during metaphase I. Inhibiting MRE11 by mirin during meiotic maturation results in anaphase bridges and also increases the number of γH2AX foci in metaphase II. Compromised DNA integrity in mirin-treated oocytes indicates a role for MRE11 in chromosome integrity during meiotic maturation.
由于低水平的DNA双链断裂（DSB）似乎不会在完全成熟的卵母细胞中激活ATM介导的减数分裂前期I检查点，因此可能存在保护减数分裂成熟过程中染色体完整性的机制。通过实时成像，我们证明了由放射模拟药物新制癌菌素（NCS）诱导的低水平DSB会增加染色体片段和落后染色体的发生率，但不会导致后期促进复合物/细胞周期体（APC/C）激活和后期起始延迟。在对照和NCS处理的卵母细胞中，由γH2AX焦点代表的DSB数量在减数分裂前期I和中期II之间显著减少。用NCS短暂处理会使减数分裂前期I卵母细胞中的DSB数量增加2倍以上，但这些卵母细胞中只有不到30%会带着分离错误进入后期。MRE11而非ATM对于检测减数分裂前期I中的DSB至关重要，并且在减数分裂中期I期间参与H2AX磷酸化。在减数分裂成熟过程中用米林抑制MRE11会导致后期桥接，并且还会增加减数分裂中期II中γH2AX焦点的数量。米林处理的卵母细胞中受损的DNA完整性表明MRE11在减数分裂成熟过程中对染色体完整性具有作用。
