MiRNA可募集許多RNA結合蛋白(RNA binding protein, RBP)，為一個相當有趣的生物現象。儘管目前學者對於RBP調控未成熟miRNA的生合成已有相當了解，而彼等對於RBP調控成熟miRNA等生物功能則未有指出。有鑑於此．本研究利用人類蛋白質體晶片(包含約17,000個蛋白質)與miRNA-122為模式，成功篩選40個miRNA-122結合蛋白。進一步對此miRNA-122結合蛋白之生物形象進行分析，共定義4個成熟的miRNA-122結合蛋白。研究利用客製建構之miRNA-122標的序列DNA晶片，並測試此4種成熟miRNA-122結合蛋白對其干擾miRNA與其標的DNA雜和顯示，hnRNPK可結合miRNA-122 (70%)或miRNA-122標的序列(30%)進而抑制miRNA-122與miRNA-122標的DNA序列之雜和。且彼等雜和之抑制可隨hnRNP K含量呈劑量反應，充分顯示hnRNP K的專一性。體內研究利用AML12細胞株並大量表現hnRNP K顯示，hnRNP K可降低miR-122對於Aldolase A的抑制作用，且不影響AML12內源miR-122的生合成。綜觀，本研究以成熟miR122為模式發現，hnRNP K可結合miR122並抑制其轉錄後之調控。本研究乃提供一新穎之miRNA調控機制，其對於miRNA領域具有重要影響。彼等研究成果可進一步用於miRNA相關疾病之治療。 MiRNA regulation is an intriguing biological process that recruits several RBPs. Although the regulation of miRNA biosynthesis has been thoroughly studied, a direct regulation through binding to mature miRNA has not been reported. Using a human proteome chip which consist of ~17.000 unique human proteins and miR-122 as a model, we identified 40 miR-122-binding proteins. After further screening by their biological profiles, four mature miR-122-binding proteins were identified. We established the DNA chip containing miR-122 target sequence to test the capability of our identified proteins to interfere the hybridization between miR-122 and its target sequence. Among the four miR-122-binding proteins, only heterogenous ribonucleoprotein K (hnRNP K) showed the most significant ability (70%) to inhibit the hybridization through binding to miR-122, while mild inhibition (30%) through binding to miR-122-targetting sequence was also observed. The hybridization inhibition was proportionally related to the amount of hnRNP K in a dose response manner, indicating the specificity of this inhibition. In vivo study, overexpression of hnRNP K in AML12 cell line significantly decreased the inhibition of miR-122 toward its target mRNA of Aldolase A without affecting the biosynthesis of miR122 itself. In summary, we hypothesized that hnRNP K exhibited a novel regulation toward miR122 by directly bind to it and inhibit its function of posttranscriptional regulation. Although further study was necessary, our finding provided a new direction of miRNA regulation study which might be important for development of miRNA-related diseases therapies.
