CHECKPOINT CONTROL OF G2 & M TRANSITION LASER MICROSURGERY STUDY

(由美国国立卫生研究院核不育系40198至C.L.里德支持)。在这项研究中，激光 显微外科手术用于确定RAD-9检查站何时打开 在脊椎动物的体细胞中。在酵母中的研究表明，有丝分裂 当染色体因辐射而受损时，就会被阻止。然而， 我们从实验室的工作中得知，脊椎动物的体细胞 不会以同样的方式回应。相反，在这些细胞中进行有丝分裂 正常情况下，当染色体被激光显微手术切除后 核包膜破裂。在目前的研究中，我们检查了 DNA和细胞质局部损伤在控制中的作用 核包膜破裂。我们发现具有破坏性的DNA 中期前期细胞将它们返回到间期，但这是相同的 对晚期前期细胞的实验不会抑制进入有丝分裂。 我们还发现，辐射诱导的早期细胞逆转 间期与组蛋白H1的去磷酸化相关， 组蛋白H3和MPM-2外延打开。这些数据是第一批 证明细胞周期是可逆的，并提出这一点 逆转是由CDK1活性下调所介导的 前期中期。Rieder，C.L.，A.Khodjakov和R.W.Cole.(1998) 前期辐射诱导的细胞周期逆转： 对年G2/M过渡的检查点控制的影响 脊椎动物。染色体分离与非整倍体 研讨会，葡萄牙波尔图，7月1日至6日。里德、C.L.和R.W.科尔 (1998年)。脊椎动物体细胞进入有丝分裂的守卫 一种染色体损伤检查点，在以下情况下逆转细胞周期 在前期早期而不是后期触发。J.细胞生物学， 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.