Positive and negative modulation of viral and cellular mRNAs by liver-specific microRNA miR-122.
microRNAs (miRNAs) are small RNAs that in general down-regulate the intracellular abundance and translation of target mRNAs. We noted that sequestration of liver-specific miR-122 by modified antisense oligonucleotides resulted in a dramatic loss of hepatitis C virus (HCV) RNA in cultured human liver cells. A binding site for miR-122 was predicted to reside close to the 5' end of the viral genome, and its functionality was tested by mutational analyses of the miRNA-binding site in viral RNA, resulting in reduced intracellular viral RNA abundance. Importantly, ectopic expression of miR-122 molecules that contained compensatory mutations restored viral RNA abundance, revealing a genetic interaction between miR-122 and the viral RNA genome. Studies with replication-defective viral RNAs demonstrated that miR-122 affected mRNA abundance by positively modulating RNA replication. In contrast, interaction of miR-122 with the 3'-noncoding region (3'NCR) of the cellular mRNA encoding the cationic amino acid transporter CAT-1 resulted in the down-regulation of CAT-1 protein abundance. These findings provide evidence that a specific miRNA can regulate distinct target mRNAs in both a positive and negative fashion. The positive role of miR-122 in viral replication suggests that this miRNA could be targeted for antiviral therapy.
Jopling
C L
CL
Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California 94305, USA.
Norman
K L
KL
Sarnow
P
P
D020413:3' Untranslated Regions; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D027201:Cationic Amino Acid Transporter 1 / Q000235:genetics; D002478:Cells, Cultured; D017124:Conserved Sequence; D015536:Down-Regulation; D016174:Hepacivirus / Q000235:genetics / Q000378:metabolism; D022781:Hepatocytes / Q000378:metabolism*; D006801:Humans; D035683:MicroRNAs / Q000235:genetics* / Q000378:metabolism*; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000235:genetics* / Q000378:metabolism*; D012367:RNA, Viral / Q000235:genetics* / Q000378:metabolism*
D020413:3' Untranslated Regions; D027201:Cationic Amino Acid Transporter 1; D035683:MicroRNAs; D012333:RNA, Messenger; D012367:RNA, Viral; C420825:SLC7A1 protein, human