Two phases of chromatin decondensation during dedifferentiation of plant cells - Distinction between competence for cell fate switch and a commitment for S phase
Two phases of chromatin decondensation during dedifferentiation of plant cells - Distinction between competence for cell fate switch and a commitment for S phase
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DOI：
10.1074/jbc.m101756200
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发表时间：
2001-06-22
影响因子：
4.8
通讯作者：
Grafi, G
中科院分区：
文献类型：
--
作者：
Zhao, J;Morozova, N;Grafi, G
细胞去分化是多细胞生物体中全能性、再生和新干细胞谱系形成的主要过程。在动物中，它通常与致癌有关。在这里，我们使用烟草原生质体（没有细胞壁的植物细胞）来研究叶肉细胞去分化过程中染色质结构的变化。使用流式细胞术和微球菌核酸酶分析，我们在细胞进入 S 期之前确定了染色质解浓缩的两个阶段。第一阶段发生在用细胞壁降解酶处理后的原生质体分离过程中，而第二阶段仅发生在用植物激素诱导原生质体重新进入细胞周期之后。在没有施加激素的情况下，原生质体经历染色质缩合/解缩合和死亡的循环。研究发现，泛素蛋白水解系统对于原生质体进入 S 期是必不可少的，是染色质去浓缩的第二阶段而非第一阶段所必需的。新兴模型表明，细胞去分化通过染色质去浓缩的两个功能不同的阶段进行：第一个阶段是赋予细胞命运转换能力的过渡阶段，在适当的条件下，接下来是第二个蛋白酶体依赖阶段，代表有丝分裂周期的承诺。这些发现可能对高等真核生物中广泛的去分化驱动的细胞过程产生影响。
Cellular dedifferentiation is the major process underlying totipotency, regeneration, and formation of new stem cell lineages in multicellular organisms, In animals it is often associated with carcinogenesis. Here, we used tobacco protoplasts (plant cells devoid of cell wall) to study changes in chromatin structure in the course of dedifferentiation of mesophyll cells. Using flow cytometry and micrococcal nuclease analyses, we identified two phases of chromatin decondensation prior to entry of cells into S phase. The first phase takes place in the course of protoplast isolation, following treatment with cell wall degrading enzymes, whereas the second occurs only after protoplasts are induced with phytohormones to re-enter the;cell cycle. In the absence of hormonal application, protoplasts undergo cycles of chromatin condensation/decondensation and die. The ubiquitin proteolytic system was found indispensable for protoplast progression into S phase, being required for the second but not the first phase of chromatin decondensation, The emerging model suggests that cellular dedifferentiation proceeds by two functionally distinct phases of chromatin decondensation: the first is a transitory phase that confers competence for cell fate switch, which is followed, under appropriate conditions, by a second proteasome dependent phase representing a commitment for the mitotic cycle. These findings might have implications for a wide range of dedifferentiation driven cellular processes in higher eukaryotes.