Tamura K, Liu H, Takahashi H
Institute of Molecular and Cellular Biosciences, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan.
J Biol Chem. 1999 Jul 23;274(30):20997-1002. doi: 10.1074/jbc.274.30.20997.
Telomerase activity was measured at each phase of the cell cycle in synchronized tobacco (Nicotiana tabacum) BY-2 cells in suspension culture with the use of the telomeric repeat amplification protocol assay. The activity was low or undetectable at most phases of the cell cycle but showed a marked increase at early S phase. The induction of telomerase activity was not affected by the S phase blockers aphidicolin (which inhibits DNA polymerase alpha) or hydroxyurea (which inhibits ribonucleotide reductase), but it was prevented by olomoucine, an inhibitor of Cdc2/Cdk2 kinases that blocks G(1)-S cell cycle transition. These results suggest that the induction of telomerase activity is not directly coupled to DNA replication by conventional DNA polymerases, but rather is triggered by the entry of cells into S phase. Various analogs of the plant hormone auxin, including indole-3-acetic acid, alpha-naphthaleneacetic acid, and 2,4-dichlorophenoxyacetic acid, potentiated the increase in telomerase activity at early S phase; the growth-inactive analog 2,3-dichlorophenoxyacetic acid, however, had no such effect. Potentiation by indole-3-acetic acid of the induction of telomerase activity was dose dependent. Together, these data indicate that telomerase activity in tobacco cells is regulated in a cell cycle-dependent manner, and that the increase in activity at S phase is specifically inducible by auxin.
利用端粒重复序列扩增协议分析法，在悬浮培养的同步化烟草（Nicotiana tabacum）BY - 2细胞的细胞周期各阶段测定端粒酶活性。在细胞周期的大多数阶段，该活性较低或无法检测到，但在S期早期显著增加。端粒酶活性的诱导不受S期阻断剂阿非迪霉素（抑制DNA聚合酶α）或羟基脲（抑制核糖核苷酸还原酶）的影响，但被olomoucine（一种Cdc2/Cdk2激酶抑制剂，可阻断G(1)-S细胞周期转换）所抑制。这些结果表明，端粒酶活性的诱导并非通过传统DNA聚合酶直接与DNA复制相关联，而是由细胞进入S期触发。包括吲哚 - 3 - 乙酸、α - 萘乙酸和2,4 - 二氯苯氧乙酸在内的各种植物激素生长素类似物，增强了S期早期端粒酶活性的增加；然而，无生长活性的类似物2,3 - 二氯苯氧乙酸则没有这种作用。吲哚 - 3 - 乙酸对端粒酶活性诱导的增强作用呈剂量依赖性。总之，这些数据表明烟草细胞中的端粒酶活性以细胞周期依赖性方式受到调节，并且S期活性的增加可被生长素特异性诱导。
