MicroRNAs (miRNAs) are ∼22 nt small noncoding RNAs that control gene expression at the posttranscriptional level through translational inhibition and destabilization of their target mRNAs. The biogenesis of miRNAs involves a series of processing steps beginning with cropping of the primary miRNA transcript by the Microprocessor complex, which is comprised of Drosha and DGCR8. Here we report a novel regulatory interaction between the Microprocessor components and coilin, the Cajal Body (CB) marker protein. Coilin knockdown causes alterations in the level of primary and mature miRNAs, let-7a and miR-34a, and their miRNA targets, HMGA2 and Notch1, respectively. We also found that coilin knockdown affects the levels of DGCR8 and Drosha in cells with (HeLa) and without (WI-38) CBs. To further explore the role of coilin in miRNA biogenesis, we conducted a series of co-immunoprecipitation experiments using coilin and DGCR8 constructs, which revealed that coilin and DGCR8 can form a complex. Additionally, our results indicate that phosphorylation of DGCR8, which has been shown to increase protein stability, is impacted by coilin knockdown. Collectively, our results implicate coilin as a member of the regulatory network governing miRNA biogenesis.

MicroRNA (miRNA) 是~22 nt 的小非编码 RNA，通过翻译抑制和破坏其靶 mRNA 的稳定性来控制转录后水平的基因表达。 miRNA 的生物发生涉及一系列处理步骤，首先是由微处理器复合体（由 Drosha 和 DGCR8 组成）裁剪初级 miRNA 转录本。在这里，我们报告了微处理器组件和线圈蛋白（Cajal Body (CB) 标记蛋白）之间的新型调节相互作用。 Coilin 敲低会导致初级和成熟 miRNA（let-7a 和 miR-34a）及其 miRNA 靶标 HMGA2 和 Notch1 水平的改变。我们还发现，coilin 敲低会影响含有 (HeLa) 和不含 (WI-38) CB 的细胞中 DGCR8 和 Drosha 的水平。为了进一步探讨coilin在miRNA生物合成中的作用，我们使用coilin和DGCR8构建体进行了一系列免疫共沉淀实验，结果表明coilin和DGCR8可以形成复合物。此外，我们的结果表明，DGCR8 的磷酸化（已被证明可以提高蛋白质稳定性）受到了线圈蛋白敲低的影响。总的来说，我们的结果表明，coilin 是调控 miRNA 生物发生的调控网络的成员。