Lysine tRNA and cell division: a G1 cell cycle mutant is temperature sensitive for the modification of tRNA5Lys to tRNA4Lys.
Lysine tRNA and cell division: a G1 cell cycle mutant is temperature sensitive for the modification of tRNA5Lys to tRNA4Lys.
复制标题
赖氨酸 tRNA 和细胞分裂：G1 细胞周期突变体对于 tRNA5Lys 至 tRNA4Lys 的修饰对温度敏感。
作者：
B. Ortwerth;V. K. Lin;J. Lewis;R. J. Wang
Ts-694是仓鼠细胞的温度敏感突变体，其在39度的限制性温度下被阻断在细胞周期的G1期。通过RPC-5色谱法比较Lys-tRNA同功受体，显示在39 ℃时tRNA5Lys减少，tRNA4Lys增加。这与在33度的允许温度下在汇合培养物中观察到的变化相同。这些Lys-tRNA的变化，没有看到在TS-694细胞在G1期阻断异亮氨酸缺乏，也没有在其他两个G1 TS突变体在限制性温度。被胸苷阻滞在S期的细胞在升高到39度时也含有降低的tRNA4Lys水平。当细胞恢复到允许温度时，tRNA4Lys水平和细胞分裂都增加。建立了以tRNA6Lys和tRNA2Lys为中间体，将tRNA5Lys修饰为tRNA4Lys的体外实验方法。第一个反应是合成tRNA6Lys，其涉及在反密码子的第三位引入修饰的尿苷。当在25 ℃下测定时，在33 ℃下生长的694细胞的提取物能够在体外将大鼠肝脏[3H] tRNA5Lys修饰为tRNA6Lys和tRNA4Lys，但在39 ℃下不能。然而，Balb/c 3T3细胞的提取物在39度下比在25度下更具活性，表明正常酶对温度不敏感。TS-694细胞tRNA，分离自细胞生长在33度，在25度和39度与大鼠肝合成酶氨酰化。在两种温度下都存在tRNA4Lys，表明ts-694细胞不含温度敏感性tRNA4Lys。
Ts-694 is a temperature sensitive mutant of hamster cells which is blocked in the G1 phase of the cell cycle at the restrictive temperature of 39 degrees. A comparison of the Lys-tRNA isoacceptors by RPC-5 chromatography showed a decrease in tRNA5Lys and an increase in tRNA4Lys at 39 degrees. This was identical to the changes seen in confluent cultures at the permissive temperature of 33 degrees. These Lys-tRNA changes were not seen in ts-694 cells blocked in G1 by isoleucine deficiency, nor in two other G1 ts mutants at the restrictive temperature. Cells trapped in S phase by a thymidine block also contained decreased levels of tRNA4Lys when raised to 39 degrees. Both tRNA4Lys levels and cell division increased when the cells were returned to the permissive temperature. An in vitro assay was established for the modification of tRNA5Lys to tRNA4Lys with tRNA6Lys and tRNA2Lys as intermediates. The first reaction is the synthesis of tRNA6Lys which involves the introduction of a modified uridine at the third position of the anticodon. Extracts of 694 cells grown at 33 degrees were able to modify rat liver [3H] tRNA5Lys to tRNA6Lys and tRNA4Lys in vitro when assayed at 25 degrees but not at 39 degrees. Extracts of Balb/c 3T3 cells, however, were more active at 39 degrees than at 25 degrees showing that the normal enzyme is not temperature sensitive. Ts-694 cell tRNA, isolated from cells grown at 33 degrees was aminoacylated at both 25 degrees and 39 degrees with rat liver synthetases. tRNA4Lys was present at both temperatures indicating that ts-694 cells do not contain a temperature sensitive tRNA4Lys.