Many eukaryotic genes generate linear mRNAs and circular RNAs, but it is largely unknown how the ratio of linear to circular RNA is controlled or modulated. Using RNAi screening in Drosophila cells, we identify many core spliceosome and transcription termination factors that control the RNA outputs of reporter and endogenous genes. When spliceosome components were depleted or inhibited pharmacologically, the steady-state levels of circular RNAs increased while expression of their associated linear mRNAs concomitantly decreased. Upon inhibiting RNA polymerase II termination via depletion of the cleavage/polyadenylation machinery, circular RNA levels were similarly increased. This is because readthrough transcripts now extend into downstream genes and are subjected to backsplicing. In total, these results demonstrate that inhibition or slowing of canonical pre-mRNA processing events shifts the steady-state output of protein-coding genes toward circular RNAs. This is in part because nascent RNAs become directed into alternative pathways that lead to circular RNA production.

许多真核基因会产生线性mRNA和环状RNA，但很大程度上未知如何控制或调节线性RNA与环状RNA的比例。在果蝇中使用RNAi筛选在细胞中，我们确定了许多核心剪接体和转录终止因子，这些因子控制着报道基因和内源基因的RNA输出。当剪接体成分在药理上被消耗或抑制时，环状RNA的稳态水平增加，而其相关线性mRNA的表达随之减少。在通过切割/聚腺苷酸化机制的耗竭抑制RNA聚合酶II终止后，环状RNA的含量也相应增加。这是因为通读转录本现在延伸到下游基因中，并进行了反向剪接。总体而言，这些结果表明，抑制或减慢规范性mRNA的前加工过程将蛋白质编码基因的稳态输出向环形RNA转移。