Mature microRNA-binding protein QKI promotes microRNA-mediated gene silencing
Kyung-Won Min,
Myung Hyun Jo,
Minseok Song,
Ji Won Lee,
Min Ji Shim,
Kyungmin Kim,
Hyun Bong Park,
Shinwon Ha,
Hyejin Mun,
Ahsan Polash,
Markus Hafner,
Jung-Hyun Cho,
Dongsan Kim,
Ji-Hoon Jeong,
Seungbeom Ko,
Sungchul Hohng,
Sung-Ung Kang,
Je-Hyun Yoon
Affiliations
Kyung-Won Min
Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC, USA
Myung Hyun Jo
Department of Physics & Astronomy, Seoul National University, Seoul, Republic of Korea
Minseok Song
Department of Physics & Astronomy, Seoul National University, Seoul, Republic of Korea
Ji Won Lee
Department of Biology, Gangneung-Wonju National University, Gangneung, Republic of Korea
Min Ji Shim
Department of Biology, Gangneung-Wonju National University, Gangneung, Republic of Korea
Kyungmin Kim
Department of Biology, Gangneung-Wonju National University, Gangneung, Republic of Korea
Hyun Bong Park
Department of Biology, Gangneung-Wonju National University, Gangneung, Republic of Korea
Shinwon Ha
Neuroregeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, USA
Hyejin Mun
Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC, USA
Ahsan Polash
Laboratory of Muscle Stem Cells and Gene Regulation, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, USA
Markus Hafner
Laboratory of Muscle Stem Cells and Gene Regulation, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, USA
Jung-Hyun Cho
Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC, USA
Dongsan Kim
Neuroregeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, USA
Ji-Hoon Jeong
Department of Oncology Science, University of Oklahoma, Oklahoma City, USA
Seungbeom Ko
Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC, USA
Sungchul Hohng
Department of Physics & Astronomy, Seoul National University, Seoul, Republic of Korea
Sung-Ung Kang
Neuroregeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, USA
Je-Hyun Yoon
Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC, USA
Although Argonaute (AGO) proteins have been the focus of microRNA (miRNA) studies, we observed AGO-free mature miRNAs directly interacting with RNA-binding proteins, implying the sophisticated nature of fine-tuning gene regulation by miRNAs. To investigate microRNA-binding proteins (miRBPs) globally, we analyzed PAR-CLIP data sets to identify RBP quaking (QKI) as a novel miRBP for let-7b. Potential existence of AGO-free miRNAs were further verified by measuring miRNA levels in genetically engineered AGO-depleted human and mouse cells. We have shown that QKI regulates miRNA-mediated gene silencing at multiple steps, and collectively serves as an auxiliary factor empowering AGO2/let-7b-mediated gene silencing. Depletion of QKI decreases interaction of AGO2 with let-7b and target mRNA, consequently controlling target mRNA decay. This finding indicates that QKI is a complementary factor in miRNA-mediated mRNA decay. QKI, however, also suppresses the dissociation of let-7b from AGO2, and slows the assembly of AGO2/miRNA/target mRNA complexes at the single-molecule level. We also revealed that QKI overexpression suppresses cMYC expression at post-transcriptional level, and decreases proliferation and migration of HeLa cells, demonstrating that QKI is a tumour suppressor gene by in part augmenting let-7b activity. Our data show that QKI is a new type of RBP implicated in the versatile regulation of miRNA-mediated gene silencing.
