RNA polymerase II CTD S2P is dispensable during embryogenesis but regulates the developmental diapause in C. elegans [RNA-seq]

We show that inactivating CDK-12 or expressing a full-length CTD S2A mutant in Caenorhabditis elegans results in developmental arrest at the L1 stage,which mimicks the diapause induced when hatching occurs in the absence of food. Transcriptomic analyses indicate that when CDK-12 is inhibited, only a subset of growth-related genes is not properly expressed. These genes correspond to SL2 trans-spliced mRNAs located in position 2 and over within operons. We show that CDK-12 is required for maximal occupancy of CstF (cleavage stimulatory factor) required for SL2 trans-splicing. The addition of food to developmentally arrested worms leads to an increase of both CTD S2P and SL2 trans-splicing. We propose that CTD S2P functions as a gene-specific signaling mark ensuring the nutritional control of C. elegans development. Overall design: RNA-seq in wild-type and CDK12-as strain, in presence of absence of CDK12-as inhibitor, for L1-arrested C.elegans cells either starved or fed during 4h post-starvation.

本研究证实，在秀丽隐杆线虫（Caenorhabditis elegans）中灭活CDK-12或表达全长羧基末端结构域（C-terminal domain, CTD）S2A突变体，可导致线虫在L1阶段发生发育停滞，该表型模拟了无食物条件下孵化时诱发的滞育状态。转录组分析显示，当CDK-12受到抑制时，仅有部分生长相关基因无法正常表达。这些基因对应于操纵子内第2位及后续位置的SL2反式剪接mRNA（SL2 trans-spliced mRNA）。本研究证实，CDK-12是SL2反式剪接所需的剪切刺激因子（cleavage stimulatory factor, CstF）达到最大结合占有率所必需的。向发育停滞的线虫添加食物后，CTD S2P磷酸化水平与SL2反式剪接效率均有所提升。本研究提出，CTD S2P可作为基因特异性信号标记，保障秀丽隐杆线虫发育的营养调控。实验整体设计：针对L1阶段停滞的秀丽隐杆线虫细胞，分别设置饥饿状态与饥饿后4小时喂食状态两种条件；在存在或不存在CDK12-as抑制剂的情况下，对野生型菌株与CDK12-as菌株开展RNA测序。