Hepato-specific microRNA-122 facilitates accumulation of newly synthesized miRNA through regulating PRKRA.

microRNAs (miRNAs) are a versatile class of non-coding RNAs involved in regulation of various biological processes. miRNA-122 (miR-122) is specifically and abundantly expressed in human liver. In this study, we employed 3′-end biotinylated synthetic miR-122 to identify its targets based on affinity purification. Quantitative RT-PCR analysis of the affinity purified RNAs demonstrated a specific enrichment of several known miR-122 targets such as CAT-1 (also called SLC7A1), ADAM17 and BCL-w. Using microarray analysis of affinity purified RNAs, we also discovered many candidate target genes of miR-122. Among these candidates, we confirmed that protein kinase, interferon-inducible double-stranded RNA-dependent activator (PRKRA), a Dicer-interacting protein, is a direct target gene of miR-122. miRNA quantitative-RT–PCR results indicated that miR-122 and small interfering RNA against PRKRA may facilitate the accumulation of newly synthesized miRNAs but did not detectably affect endogenous miRNAs levels. Our findings will lead to further understanding of multiple functions of this hepato-specific miRNA. We conclude that miR-122 could repress PRKRA expression and facilitate accumulation of newly synthesized miRNAs.

微小RNA（miRNAs）是一类具有多种功能的非编码RNA，参与多种生物过程的调控。miR - 122在人肝脏中特异性高表达。在本研究中，我们利用3′端生物素化的合成miR - 122，基于亲和纯化来鉴定其靶标。对亲和纯化的RNA进行定量逆转录聚合酶链反应（RT - PCR）分析表明，几种已知的miR - 122靶标，如阳离子氨基酸转运蛋白1（也称为SLC7A1）、去整合素金属蛋白酶17（ADAM17）和B细胞淋巴瘤蛋白w（BCL - w）有特异性富集。通过对亲和纯化的RNA进行微阵列分析，我们还发现了许多miR - 122的候选靶基因。在这些候选基因中，我们证实蛋白激酶、干扰素诱导的双链RNA依赖的激活因子（PRKRA），一种与Dicer相互作用的蛋白，是miR - 122的一个直接靶基因。miRNA定量逆转录聚合酶链反应结果表明，miR - 122和针对PRKRA的小干扰RNA可能促进新合成的miRNAs的积累，但对内源性miRNAs水平没有可检测到的影响。我们的研究结果将有助于进一步了解这种肝脏特异性miRNA的多种功能。我们得出结论，miR - 122可以抑制PRKRA的表达并促进新合成的miRNAs的积累。