ERH facilitates microRNA maturation through the interaction with the N-terminus of DGCR8

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• MicroRNA (miRNA) biogenesis is initiated by the Microprocessor complex, comprising DROSHA and DGCR8.
• This complex processes primary miRNA (pri-miRNA) transcripts to facilitate miRNA maturation.
• The precise regulation of Microprocessor activity, especially for suboptimal substrates, remains an area of investigation.

Purpose of the Study:

• To identify novel components of the Microprocessor complex.
• To elucidate the structural and functional role of Enhancer of Rudimentary Homolog (ERH) in miRNA biogenesis.
• To understand how ERH influences the processing of pri-miRNAs, particularly within polycistronic clusters.

Main Methods:

• Crystal structure determination of the ERH-DGCR8 interaction.
• Biochemical assays to assess binding stoichiometry and affinity.
• RNA immunoprecipitation and quantitative PCR to analyze pri-miRNA processing.
• RNA interference (RNAi) and CRISPR-Cas9 gene editing to knock down ERH or DGCR8.

Main Results:

• Enhancer of Rudimentary Homolog (ERH) was identified as a novel component of the Microprocessor complex.
• Structural and biochemical data revealed ERH binds DGCR8 in a 2:2 stoichiometry via a hydrophobic groove.
• ERH depletion or DGCR8 N-terminal deletion impaired processing of suboptimal pri-miRNAs in clusters.
• ERH demonstrated a cluster-assistance mechanism, enhancing processing of pri-miR-451 dependent on pri-miR-144.

Conclusions:

• ERH is a functional component of the Microprocessor complex, essential for efficient miRNA biogenesis.
• ERH mediates a 'cluster assistance' mechanism, facilitating the processing of suboptimal pri-miRNAs.
• This discovery provides new insights into the regulation of miRNA processing and the role of accessory factors in RNA maturation pathways.