Center for Stem Cell Biology and Tissue Engineering, Key Laboratory for Stem Cells and Tissue Engineering, Ministry of Education, Sun Yat-sen University , Guangzhou , China.
RNA Biomedical Institute, Sun Yat-sen Memorial Hospital, Sun Yat-sen University , Guangzhou , China.
RNA Biol. 2019 Oct;16(10):1448-1460. doi: 10.1080/15476286.2019.1636596. Epub 2019 Jul 7.
It is increasingly appreciated that U1 snRNP transcriptomically suppresses the usage of intronic polyadenylation site (PAS) of mRNAs, an outstanding question is why frequently used PASs are not suppressed. Here we found that U1 snRNP could be transiently associated with sequences upstream of actionable PASs in human cells, and RNA-RNA interaction might contribute to the association. By focusing on individual PAS, we showed that the stable assembly of U1 snRNP near PAS might be generally required for U1 inhibition of mRNA 3' processing. Therefore, actionable PASs that often lack optimal U1 snRNP docking site nearby is free from U1 inhibitory effect. Consistently, natural 5' splicing site (5'-SS) is moderately enriched ~250 nt upstream of intronic PASs whose usage is sensitive to functional knockdown of U1 snRNA. Collectively, our results provided an insight into how U1 snRNP selectively inhibits the usage of PASs in a cellular context, and supported a prevailing model that U1 snRNP scans pre-mRNA through RNA-RNA interaction to find a stable interaction site to exercise its function in pre-mRNA processing, including repressing the usage of cryptic PASs.
越来越多的人认识到 U1 snRNP 在转录水平上抑制了 mRNA 内含子多聚腺苷酸化位点（PAS）的使用，但一个悬而未决的问题是，为什么经常使用的 PAS 没有被抑制。在这里，我们发现 U1 snRNP 可以在人类细胞中转录物上与有作用的 PAS 上游序列短暂结合，RNA-RNA 相互作用可能有助于这种结合。通过关注单个 PAS，我们表明 U1 snRNP 在 PAS 附近的稳定组装通常是 U1 抑制 mRNA 3' 加工所必需的。因此，附近缺乏最佳 U1 snRNP docking 位点的有作用的 PAS 不受 U1 抑制作用的影响。一致地，天然 5' 剪接位点（5'-SS）在内含子 PAS 上游适度富集~250nt，其使用对 U1 snRNA 功能缺失的敏感性。总的来说，我们的结果提供了一个见解，即 U1 snRNP 如何在细胞环境中选择性地抑制 PAS 的使用，并支持一个流行的模型，即 U1 snRNP 通过 RNA-RNA 相互作用来扫描 pre-mRNA，以找到一个稳定的相互作用位点来行使其在 pre-mRNA 加工中的功能，包括抑制隐式 PAS 的使用。
