The spliceosome is a large ribonucleoprotein complex that catalyzes the removal of introns from RNA polymerase II-transcribed RNAs. Spliceosome assembly occurs in a stepwise manner through specific intermediates referred to as pre-spliceosome complexes E, A, B, B* and C. It has been reported that small molecule inhibitors of the spliceosome that target the SF3B1 protein component of complex A lead to the accumulation of cells in the G₁ and G₂/M phases of the cell cycle. Here we performed a comprehensive flow cytometry analysis of the effects of isoginkgetin (IGG), a natural compound that interferes with spliceosome assembly at a later step, complex B formation. We found that IGG slowed cell cycle progression in multiple phases of the cell cycle (G₁, S and G₂) but not M phase. This pattern was somewhat similar to but distinguishable from changes associated with an SF3B1 inhibitor, pladienolide B (PB). Both drugs led to a significant decrease in nascent DNA synthesis in S phase, indicative of an S phase arrest. However, IGG led to a much more prominent S phase arrest than PB while PB exhibited a more pronounced G₁ arrest that decreased the proportion of cells in S phase as well. We also found that both drugs led to a comparable decrease in the proportion of cells in M phase. This work indicates that spliceosome inhibitors affect multiple phases of the cell cycle and that some of these effects vary in an agent-specific manner despite the fact that they target splicing at similar stages of spliceosome assembly.

剪接体是大的核糖核蛋白复合物，它催化从RNA聚合酶II转录的RNA中去除内含子。剪接体组装通过称为中间剪接体复合体E，A，B，B *和C的特定中间体以逐步方式发生。据报道，靶向复合体A的SF3B1蛋白成分的剪接体小分子抑制剂可导致在细胞周期的G ₁和G ₂ / M期细胞的积累。在这里，我们对异格格丁素（IGG）的作用进行了全面的流式细胞术分析，这是一种天然化合物，在以后的步骤中会干扰复合体的组装，即复杂的B形成。我们发现IGG在细胞周期的多个阶段（G ₁，S和G₂）但不是M相。该模式与SF3B1抑制剂普拉二烯内酯B（PB）相关的变化有些相似，但有区别。两种药物均导致S期新生DNA合成显着减少，表明S期停滞。但是，IGG导致S期阻滞比PB更为明显，而PB表现出更明显的G ₁阻滞，这也降低了S期的细胞比例。我们还发现，两种药物均导致M期细胞比例的下降。这项工作表明剪接体抑制剂会影响细胞周期的多个阶段，尽管这些作用的目标是在剪接体组装的相似阶段进行剪接，但其中某些作用仍以试剂特异性方式变化。