Sehgal P B, Derman E, Molloy G R, Tamm I, Darnell J E
Science. 1976 Oct 22;194(4263):431-3. doi: 10.1126/science.982026.
The nucleoside analog 5, 6-dichloro-1-beta-d-ribofuranosylbenzimidazole (DRB) at 75 to 150 micromolar concentrations inhibits the synthesis of nuclear heterogeneous RNA (hnRNA) in HeLa cells by 60 to 70 percent. The sedimentation profile of hnRNA labeled with (3H)uridine for 45 seconds after brief treatment (45, 90, or 180 seconds) with DRB showed a progressive decrease in the labeling of shorter hnRNA molecules relative to longer molecules. Prior exposure of the cells to actinomycin D, an inhibitor of RNA chain elongation, did not alter the sedimentation profile of hnRNA. These results suggest that DRB preferentially inhibits the initiation of hnRNA chains so that after exposure to DRB for a brief period the longer nascent chains still remain to be finished and thus incorporate a greater share of the pulse label. By progressively increasing the time of exposure to DRB, and measuring the rate of increase in the average size of the labeled, nascent RNA, it was estimated that the chains were growing at rates between 50 and 100 nucleotides per second.
核苷类似物5,6 - 二氯 - 1 -β - D - 呋喃核糖基苯并咪唑（DRB）在75至150微摩尔浓度下可抑制HeLa细胞中核不均一RNA（hnRNA）的合成达60%至70%。在用DRB进行短暂处理（45、90或180秒）后，用（3H）尿苷标记45秒的hnRNA沉降图谱显示，相对于较长分子，较短hnRNA分子的标记逐渐减少。细胞预先暴露于RNA链延伸抑制剂放线菌素D，并未改变hnRNA的沉降图谱。这些结果表明，DRB优先抑制hnRNA链的起始，因此在短暂暴露于DRB后，较长的新生链仍有待完成，从而掺入了更大比例的脉冲标记。通过逐步增加暴露于DRB的时间，并测量标记的新生RNA平均大小的增加速率，估计链的生长速率为每秒50至100个核苷酸。
