Choudhary Bikash, Norris Adam
University of California, Riverside. Department of Biochemistry.
University of California, Riverside. Department of Biochemistry. 3401 Watkins Drive, Boyce Hall, Riverside, CA, 92521, United States.
bioRxiv. 2024 Sep 26:2024.09.26.615222. doi: 10.1101/2024.09.26.615222.
Microexons (exons ≤30 nts) are important features of neuronal transcriptomes, but pose mechanistic challenges to the splicing machinery. We previously showed that PRP-40, a component of the U1 spliceosome, is globally required for microexon splicing in . Here we show that the homologous PRPF40A is also globally required for microexon splicing in mouse neuroblastoma cells. We find that PRPF40A co-regulates microexons along with SRRM4, a neuron-specific regulator of microexon splicing. The relationship between exon size and dependence on PRPF40A/SRRM4 is distinct, with SRRM4-dependence exhibiting a size threshold (~30 nts) and PRPF40A-dependence exhibiting a graded decrease as exon size increases. Finally, we show that PRPF40A knockdown causes an increase in productive splicing of its spliceosomal binding partner by skipping of a small "poison exon." Similar homeostatic cross-regulation is often observed across paralogous RNA binding proteins. Here we find this concept likewise applies across evolutionarily unrelated but functionally and physically coupled spliceosomal components.
微小外显子（外显子长度≤30个核苷酸）是神经元转录组的重要特征，但对剪接机制提出了机制上的挑战。我们之前表明，U1剪接体的一个组成部分PRP - 40在[具体生物]中对于微小外显子剪接是全局必需的。在此我们表明，同源的PRPF40A在小鼠神经母细胞瘤细胞中对于微小外显子剪接同样是全局必需的。我们发现PRPF40A与SRRM4共同调节微小外显子，SRRM4是微小外显子剪接的神经元特异性调节因子。外显子大小与对PRPF40A/SRRM4的依赖性之间的关系是不同的，对SRRM4的依赖性表现出一个大小阈值（约30个核苷酸），而对PRPF40A的依赖性随着外显子大小增加呈逐渐下降。最后，我们表明敲低PRPF40A会通过跳过一个小的“毒性外显子”导致其剪接体结合伙伴的有效剪接增加。在同源RNA结合蛋白中经常观察到类似的稳态交叉调节。在此我们发现这个概念同样适用于进化上不相关但在功能和物理上偶联的剪接体组分。
