A Macrocyclic Peptide Ligand Binds the Oncogenic MicroRNA-21 Precursor and Suppresses Dicer Processing.

MicroRNAs (miRNAs) help orchestrate cellular growth and survival through post-transcriptional mechanisms. The dysregulation of miRNA biogenesis can lead to cellular growth defects and chemotherapeutic resistance and plays a direct role in the development of many chronic diseases. Among these RNAs, miR-21 is consistently overexpressed in most human cancers, leading to the down-regulation of key tumor-suppressing and pro-apoptotic factors, suggesting that inhibition of miR-21 biogenesis could reverse these negative effects.

Targeted inhibition of oncogenic miR-21 maturation with designed RNA-binding proteins.

The RNA recognition motif (RRM) is the largest family of eukaryotic RNA-binding proteins. Engineered RRMs with well-defined specificity would provide valuable tools and an exacting test of the current understanding of specificity. We have redesigned the specificity of an RRM using rational methods and demonstrated retargeting of its activity in cells.

Rbfox proteins regulate microRNA biogenesis by sequence-specific binding to their precursors and target downstream Dicer.

Rbfox proteins regulate tissue-specific splicing by targeting a conserved GCAUG sequence within pre-mRNAs. We report here that sequence-specific binding of the conserved Rbfox RRM to miRNA precursors containing the same sequence motif in their terminal loops, including miR-20b and miR-107, suppresses their nuclear processing. The structure of the complex between precursor miR-20b and Rbfox RRM shows the molecular basis for recognition, and reveals changes in the stem-loop upon protein binding.