Stubna Michael W, Shukla Aditi, Bartel David P
Howard Hughes Medical Institute, Cambridge, Massachusetts 02142, USA.
Whitehead Institute for Biomedical Research, Cambridge, Massachusetts 02142, USA.
RNA. 2024 Dec 16;31(1):51-66. doi: 10.1261/rna.080276.124.
MicroRNAs (miRNAs) associate with Argonaute (AGO) proteins to form complexes that direct mRNA repression. miRNAs are also the subject of regulation. For example, some miRNAs are destabilized through a pathway in which pairing to specialized transcripts recruits the ZSWIM8 E3 ubiquitin ligase, which polyubiquitinates AGO, leading to its degradation and exposure of the miRNA to cellular nucleases. Here, we found that 22 miRNAs in are sensitive to loss of EBAX-1, the ZSWIM8 ortholog in nematodes, implying that these 22 miRNAs might be subject to this pathway of target-directed miRNA degradation (TDMD). The impact of EBAX-1 depended on the developmental stage, with the greatest effect on the miRNA pool (14.5%) observed in L1 larvae, and the greatest number of different miRNAs affected (17) observed in germline-depleted adults. The affected miRNAs included the miR-35-42 family, as well as other miRNAs among the least stable in the worm, suggesting that TDMD is a major miRNA-destabilization pathway in the worm. The excess miR-35-42 molecules that accumulated in mutants caused increased repression of their predicted target mRNAs and underwent 3' trimming over time. In general, however, miRNAs sensitive to EBAX-1 loss had no consistent pattern of either trimming or tailing. Replacement of the 3' region of miR-43 substantially reduced EBAX-1 sensitivity, a result that differed from that observed previously for miR-35. Together, these findings broaden the implied biological scope of TDMD-like regulation of miRNA stability in animals, and indicate that a role for miRNA 3' sequences is variable in the worm.
微小RNA（miRNA）与AGO蛋白结合形成指导mRNA抑制的复合物。miRNA也是调控的对象。例如，一些miRNA通过一种途径变得不稳定，在该途径中，与特定转录本配对会招募ZSWIM8 E3泛素连接酶，该酶对AGO进行多聚泛素化，导致其降解并使miRNA暴露于细胞核酸酶。在这里，我们发现线虫中ZSWIM8的直系同源物EBAX - 1缺失时，22种miRNA敏感，这意味着这22种miRNA可能受这种靶向miRNA降解（TDMD）途径的影响。EBAX - 1的影响取决于发育阶段，在L1幼虫中观察到对miRNA池的影响最大（14.5%），在生殖系缺失的成虫中观察到受影响的不同miRNA数量最多（17种）。受影响的miRNA包括miR - 35 - 42家族，以及线虫中最不稳定的其他一些miRNA，这表明TDMD是线虫中主要的miRNA不稳定途径。在ebax - 1突变体中积累的过量miR - 35 - 42分子导致其预测靶mRNA的抑制增加，并随时间发生3'端修剪。然而，一般来说，对EBAX - 1缺失敏感的miRNA在修剪或加尾方面没有一致的模式。替换miR - 43的3'区域可大幅降低EBAX - 1敏感性，这一结果与之前观察到的miR - 35不同。总之，这些发现拓宽了动物中类似TDMD的miRNA稳定性调控所涉及的生物学范围，并表明miRNA 3'序列在蠕虫中的作用是可变的。
