S PHASE-SPECIFIC SYNTHESIS OF DIHYDROFOLATE-REDUCTASE IN CHINESE-HAMSTER OVARY CELLS
S PHASE-SPECIFIC SYNTHESIS OF DIHYDROFOLATE-REDUCTASE IN CHINESE-HAMSTER OVARY CELLS
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DOI：
10.1073/pnas.78.8.4985
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发表时间：
1981-01-01
期刊：
影响因子：
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通讯作者：
SCHIMKE, RT
中科院分区：
文献类型：
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作者：
MARIANI, BD;SLATE, DL;SCHIMKE, RT
本文研究了二氢叶酸还原酶（DHFR）水平对经有丝分裂选择同步化的中国仓鼠卵巢细胞中蛋氨酸耐药细胞的细胞周期调控。通过标准生物化学技术和利用荧光激活细胞分选仪的双重荧光染色，在整个细胞周期中分析DNA含量和DHFR浓度。发现DHFR生物合成活性存在一个S期特异期，从S期的第2小时开始，持续到整个S期，DHFR比活性增加90%。这是由. apprxeq产生的。2.5-DHFR的水平增加一倍，而总可溶性蛋白在同一时期增加50%。这种增加是在细胞生理上致力于DNA复制后开始的DHFR分子的新合成的结果。DHFR活性在S期的增加与[3 H]胸苷掺入率的增加在相同的时间间隔内是平行的。DHFR活性的最大峰值与DNA合成的最大速率一致，这两种活性都发生在6.5小时S期的最后阶段内的大量DNA复制期间。
The cell cycle modulation of dihydrofolate reductase (DHFR) levels in methotrexate-resistant Chinese hamster ovary cells syndchronized by mitotic selection was investigated. DNA content and DHFR concentration were analyzed throughout the cell cycle by standard biochemical techniques and by double fluorescence staining utilizing the fluorescence-activated cell sorter. An S phase-specific period of DHFR biosynthetic activity was found. Commencing within hour 2 of S phase and continuing throughout the duration of S phase, there is a 90% increase in DHFR specific activity. This results from an .apprxeq. 2.5-fold increase in the level of DHFR, while total soluble protein increases 50% during the same period. This increase is the result of new synthesis of DHFR molecules initiated after the cell is physiologically committed to DNA replication. This increase in DHFR activity through S phase parallels the increasing rate of [3H]thymidine incorporation during the same interval. The maximum peak of DHFR activity is coincident with the maximum rate of DNA synthesis, both activities occurring during the bulk of DNA replication within the last stages of the 6.5-h S phase.