Lisheng Dai, Kevin Chen, Brenda Youngren, Julia Kulina, Acong Yang, Zhengyu Guo, Jin Li, Peng Yu, and Shuo Gu. “Cytoplasmic Drosha activity generated by alternative splicing,” Nucleic Acids Research (2016). doi:10.1093/nar/gkw668

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RNase III enzyme Drosha interacts with DGCR8 to form the Microprocessor, initiating canonical microRNA (miRNA) maturation in the nucleus. Here, we re-evaluated where Drosha functions in cells using Drosha and/or DGCR8 knock out (KO) cells and cleavage reporters. Interestingly, a truncated Drosha mutant located exclusively in the cytoplasm cleaved pri-miRNA effectively in a DGCR8-dependent manner. In addition, we demonstrated that in vitro generated pri-miRNAs when transfected into cells could be processed to mature miRNAs in the cytoplasm. These results indicate the existence of cytoplasmic Drosha (c-Drosha) activity. Although a subset of endogenous pri-miRNAs become enriched in the cytoplasm of Drosha KO cells, it remains unclear whether pri-miRNA processing is the main function of c-Drosha. We identified two novel in-frame Drosha isoforms generated by alternative splicing in both HEK293T and HeLa cells. One isoform loses the putative nuclear localization signal, generating c-Drosha. Further analysis indicated that the c-Drosha isoform is abundant in multiple cell lines, dramatically variable among different human tissues and upregulated in multiple tumors, suggesting that c-Drosha plays a unique role in gene regulation. Our results reveal a new layer of regulation on the miRNA pathway and provide novel insights into the ever-evolving functions of Drosha.

Nucleic Acids Research Article Link

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I’m Kevin Chen, and this is my personal website. I am a rising final-year student in the CS department at the University of Maryland. ¶ My research interests are in machine learning and theoretical computer science. I enjoy reading, filmmaking, tennis and helping out with Bitcamp.


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