CHECKPOINT CONTROL OF G2 & M TRANSITION LASER MICROSURGERY STUDY

（由NIH GMS 40198支持。L.里德尔）。 在这项研究中， 显微外科手术被用来确定RAD-9检查点何时转向 在脊椎动物体细胞中。 对酵母的研究表明有丝分裂 当染色体被辐射破坏时， 然而，在这方面， 我们从实验室的工作中得知，脊椎动物的体细胞 不以同样的方式回应。 相反，在这些细胞中， 通常，当染色体被激光显微手术切断后， 核膜破裂 在目前的研究中，我们检查了 DNA和细胞质的局部损伤在控制 核膜破裂 我们发现， 中前期细胞将它们返回到间期，但同样 对晚期前期细胞的实验不抑制进入有丝分裂。 我们还发现，辐射诱导的逆转的前期细胞， 与组蛋白H1的去磷酸化相关， 组蛋白H3和MPM-2表位。 这些数据是第一个 证明细胞周期是可逆的，并表明这一点， 逆转是由CDK 1活性的下调介导的， 中期前期 里德尔角L.，A. Khodjakov和R.W.科尔。 04 The Dog（1998） 辐射诱导的前期细胞周期逆转： G2/M转换的检查点控制的含义 脊椎动物 染色体分离与非整倍性。 讲习班，葡萄牙波尔图，7月1日至6日。 里德尔角L.和R.W.科尔 （1998年）。 脊椎动物体细胞进入有丝分裂是由 一个染色体损伤检查点，当细胞分裂时， 在早期而不是晚期的前期触发。 细胞生物学杂志， 142：1-10。

(Supported by NIH GMS 40198 to C. L. Rieder). In this study laser microsurgery was used to determine when the RAD-9 checkpoint is turned off in vertebrate somatic cells. Studies in yeast reveal that mitosis is arrested when the chromosomes are damaged by irradiation. However, we know from work in our laboratory that vertebrate somatic cells do not respond the same way. Rather, in these cells mitosis proceeds normally when the chromosomes are severed by laser microsurgery after nuclear envelope breakdown. In the current study we examined the effect of localized damage to the DNA and cytoplasm in controlling nuclear envelope breakdown. We found that damaging DNA in mid-prophase cells returns them to interphase, but that the same experiment on late prophase cells does not inhibit entry into mitosis. We also found that the radiation induced reversion of prophase cells to interphase correlates with the dephosphorylation of histone H1, histone H3 and the MPM-2 epit opes. Th ese data are the first to demonstrate that the cell cycle is reversible, and suggest that this reversion is mediated by a down-regulation of CDK1 activity during mid-prophase. Rieder, C. L., A. Khodjakov and R.W. Cole. (1998) The radiation-induced reversal of the cell cycle during prophase: Implications for the checkpoint control of the G2/M transition in vertebrates. Chromosome Segregation and Aneuploidy 4th Internat. Workshop, Porto, Portugal, July 1-6. Rieder, C. L. and R.W. Cole (1998). Entry into mitosis in vertebrate somatic cells is guarded by a chromosome damage checkpoint that reverses the cell cycle when triggered during early but not late prophase. J. Cell Biolgy, 142:1-10.