Lee Dooyoung, Nam Jin-Wu, Shin Chanseok
Department of Agricultural Biotechnology, Seoul National University, Seoul 08826, Republic of Korea.
Department of Life Science, Hanyang University, Seoul 04763, Republic of Korea.
RNA. 2017 Jul;23(7):1035-1047. doi: 10.1261/rna.059808.116. Epub 2017 Apr 11.
The nuclear RNase III enzyme DROSHA interacts with its cofactor DGCR8 to form the Microprocessor complex, which initiates microRNA (miRNA) maturation by cleaving hairpin structures embedded in primary transcripts. Apart from its central role in the biogenesis of miRNAs, DROSHA is also known to recognize and cleave miRNA-like hairpins in a subset of transcripts without apparent small RNA production. Here, we report that the human transcript is one such noncanonical target of DROSHA. Mammalian genes have evolved a conserved hairpin structure spanning a specific exon-intron junction, which serves as a substrate for the Microprocessor in human cells but not in murine cells. We show that it is this hairpin element that decides whether the overlapping exon is alternatively or constitutively spliced. We further demonstrate that DROSHA promotes skipping of the overlapping exon in human cells independently of its cleavage function. Our findings add to the expanding list of noncanonical DROSHA functions.
核核糖核酸酶III（RNase III）DROSHA与其辅助因子DGCR8相互作用形成微处理器复合物，该复合物通过切割初级转录本中嵌入的发夹结构来启动微小RNA（miRNA）的成熟过程。除了在miRNA生物合成中的核心作用外，DROSHA还已知能够识别并切割转录本子集中的miRNA样发夹结构，而不会产生明显的小RNA。在此，我们报告人类转录本是DROSHA的此类非经典靶点之一。哺乳动物基因进化出了一种保守的发夹结构，跨越特定的外显子-内含子连接，该结构在人类细胞中作为微处理器的底物，但在鼠细胞中则不然。我们表明，正是这种发夹元件决定了重叠外显子是可变剪接还是组成性剪接。我们进一步证明，DROSHA在人类细胞中促进重叠外显子的跳跃，而与其切割功能无关。我们的发现增加了DROSHA非经典功能的不断扩大的列表。
