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Updated: Feb 14, 2026

Combining Chemical Cross-linking and Mass Spectrometry of Intact Protein Complexes to Study the Architecture of Multi-subunit Protein Assemblies
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MAC3A and MAC3B, Two Core Subunits of the MOS4-Associated Complex, Positively Influence miRNA Biogenesis

Shengjun Li1,2,3, Kan Liu2,3, Bangjun Zhou2,4

  • 1Qingdao Engineering Research Center of Biomass Resources and Environment, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao 266101, China.

The Plant Cell
|February 14, 2018
PubMed

Insights

Arabidopsis MAC3A and MAC3B proteins are essential for microRNA (miRNA) biogenesis. These MOS4-associated complex (MAC) subunits stabilize primary miRNA transcripts and promote DCL1 complex activity, controlling miRNA levels.

Area of Science:

  • Plant Molecular Biology
  • Gene Regulation
  • Biochemistry

Background:

  • MOS4-associated complex (MAC) subunits MAC3A and MAC3B are conserved eukaryotic proteins.
  • Their specific roles in plant immunity and development in Arabidopsis thaliana are not fully understood.
  • Understanding their function is crucial for deciphering complex regulatory pathways.

Purpose of the Study:

  • To elucidate the functional mechanisms of Arabidopsis MAC3A and MAC3B in microRNA (miRNA) biogenesis.
  • To investigate the involvement of MAC subunits in miRNA processing and stability.
  • To determine the interaction of MAC proteins with key components of the miRNA maturation pathway.

Main Methods:

  • Analysis of miRNA accumulation in *mac3a mac3b* double mutants.
  • Measurement of primary miRNA transcript (pri-miRNA) levels.
  • Assessment of *MIR* gene promoter activity.
  • In vivo association studies of MAC3A with pri-miRNAs.
  • Investigation of interactions between MAC3A/MAC3B and the DCL1 complex components.

Main Results:

  • Loss of MAC3A and MAC3B function in *mac3a mac3b* mutants reduces miRNA accumulation and increases target transcript levels.
  • pri-miRNA levels are decreased in *mac3a mac3b* mutants, but *MIR* gene promoter activity is unaffected.
  • MAC3A and MAC3B associate with pri-miRNAs, suggesting a role in pri-miRNA stabilization.
  • MAC3A and MAC3B interact with the DCL1 complex, enhance its activity, and are necessary for HYL1 localization.
  • Other MAC subunits, CDC5 and PRL1, also participate in miRNA biogenesis.

Conclusions:

  • Arabidopsis MAC3A and MAC3B function redundantly in miRNA biogenesis.
  • The MAC complex plays a critical role in controlling miRNA levels by modulating pri-miRNA transcription, processing, and stability.
  • MAC proteins are essential regulators of miRNA homeostasis, impacting plant development and immunity.

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