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Updated: Jul 10, 2025

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JANUS, a spliceosome-associated protein, promotes miRNA biogenesis in Arabidopsis

Mu Li1,2, Huihui Yu1,2, Bangjun Zhou1,2

  • 1Center for Plant Science Innovation, University of Nebraska-Lincoln, Lincoln, NE 68588-0666, USA.

Nucleic Acids Research
|November 23, 2023
PubMed

Insights

JANUS, a splicing factor, is crucial for microRNA (miRNA) accumulation by promoting the microprocesser complex (MC) assembly and activity. It also regulates pri-miRNA transcription, revealing a novel role in miRNA biogenesis.

Area of Science:

  • Molecular Biology
  • Genetics
  • RNA Biology

Background:

  • MicroRNAs (miRNAs) are key gene expression regulators.
  • Their levels are controlled by the microprocesser complex (MC).

Purpose of the Study:

  • To investigate the role of JANUS, a U2 snRNP assembly factor, in miRNA biogenesis.
  • To elucidate JANUS's mechanism in regulating miRNA levels.

Main Methods:

  • Investigated JANUS's association with MC components (Dicer-like 1 [DCL1] and SERRATE [SE]).
  • Analyzed the effect of a hypomorphic janus mutant on MC activity and pri-miRNA processing.
  • Examined JANUS's role in pri-miRNA transcription and splicing.

Main Results:

  • JANUS associates with DCL1 and SE, and binds pri-miRNA stem-loops.
  • In janus mutants, DCL1 activity, MC numbers, and pri-miRNA-MC interactions are reduced.
  • JANUS modulates pri-miRNA transcription by facilitating Pol II occupancy.
  • Global splicing defects were observed in janus mutants.

Conclusions:

  • JANUS is essential for miRNA accumulation by promoting MC assembly and activity.
  • JANUS acts as a novel splicing factor involved in miRNA biogenesis.
  • JANUS plays a dual role in miRNA regulation, affecting both processing and transcription.

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