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miRNPs: a novel class of ribonucleoproteins containing numerous microRNAs
Zissimos Mourelatos1, Josée Dostie, Sergey Paushkin
1Howard Hughes Medical Institute, Department of Biochemistry & Biophysics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6148, USA.
Abstract:
Gemin3 is a DEAD-box RNA helicase that binds to the Survival of Motor Neurons (SMN) protein and is a component of the SMN complex, which also comprises SMN, Gemin2, Gemin4, Gemin5, and Gemin6. Reduction in SMN protein results in Spinal muscular atrophy (SMA), a common neurodegenerative disease. The SMN complex has critical functions in the assembly/restructuring of diverse ribonucleoprotein (RNP) complexes. Here we report that Gemin3 and Gemin4 are also in a separate complex that contains eIF2C2, a member of the Argonaute protein family. This novel complex is a large approximately 15S RNP that contains numerous microRNAs (miRNAs). We describe 40 miRNAs, a few of which are identical to recently described human miRNAs, a class of small endogenous RNAs. The genomic sequences predict that miRNAs are likely to be derived from larger precursors that have the capacity to form stem-loop structures.
Insights
Gemin3 and Gemin4 proteins are part of a novel complex containing microRNAs (miRNAs) and Argonaute protein eIF2C2. This finding expands our understanding of RNA processing and its link to neurodegenerative diseases like Spinal Muscular Atrophy (SMA).
Area of Science:
- Molecular Biology
- Neuroscience
- Genetics
Background:
- Gemin3 is a DEAD-box RNA helicase and a component of the Survival of Motor Neurons (SMN) complex.
- Reduced SMN protein causes Spinal Muscular Atrophy (SMA), a neurodegenerative disease.
- The SMN complex is crucial for assembling ribonucleoprotein (RNP) complexes.
Purpose of the Study:
- To investigate the cellular localization and complex formation of Gemin3 and Gemin4 beyond the SMN complex.
- To identify novel protein and RNA interactions involving Gemin3 and Gemin4.
- To explore potential roles in microRNA biogenesis and function.
Main Methods:
- Co-immunoprecipitation assays to identify interacting proteins.
- Biochemical fractionation and size exclusion chromatography to characterize RNP complexes.
- Bioinformatic analysis of genomic sequences to predict miRNA precursor structures.
Main Results:
- Gemin3 and Gemin4 were found in a distinct approximately 15S RNP complex.
- This novel complex includes eIF2C2, an Argonaute family protein.
- The complex contains at least 40 different microRNAs (miRNAs), including known human miRNAs.
- Genomic analysis suggests miRNAs originate from stem-loop forming precursors.
Conclusions:
- Gemin3 and Gemin4 participate in at least two distinct cellular complexes.
- A novel RNP complex involving Gemin3, Gemin4, eIF2C2, and numerous miRNAs has been identified.
- This discovery provides new insights into miRNA processing and regulation, potentially relevant to SMA pathogenesis.