MAC5 is a component of the conserved MOS4-associated complex. It plays critical roles in development and immunity. Here we report that MAC5 is required for microRNA (miRNA) biogenesis. MAC5 interacts with Serrate (SE), which is a core component of the microprocessor that processes primary miRNA transcripts (pri-miRNAs) into miRNAs and binds the stem-loop region of pri-miRNAs. MAC5 is essential for both the efficient processing and the stability of pri-miRNAs. Interestingly, the reduction of pri-miRNA levels in mac5 is partially caused by XRN2/XRN3, the nuclear-localized 5′-to-3′ exoribonucleases, and depends on SE. These results reveal that MAC5 plays a dual role in promoting pri-miRNA processing and stability through its interaction with SE and/or pri-miRNAs. This study also uncovers that pri-miRNAs need to be protected from nuclear RNA decay machinery, which is connected to the microprocessor.

MAC5是与MOS4相关的保守复合体的组成部分。它在发育和免疫中起关键作用。在这里我们报告说，microRNA（miRNA）生物发生需要MAC5。MAC5与Serrate（SE）相互作用，后者是微处理器的核心组件，该处理器将原始miRNA转录本（pri-miRNA）处理为miRNA，并结合pri-miRNA的茎环区域。MAC5对于pri-miRNA的有效加工和稳定性至关重要。有趣的是，mac5中pri-miRNA水平的降低部分由XRN2 / XRN3（核定位的5'至3'核糖核酸外切酶）引起，并取决于SE。这些结果表明，MAC5通过与SE和/或pri-miRNA相互作用，在促进pri-miRNA加工和稳定性方面起着双重作用。这项研究还发现，必须保护pri-miRNA免受连接到微处理器的核RNA衰变机制的侵害。