Plant Science Innovation, Center for


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Nucleic Acids Research , 2024, 52 , 420–430


Open access.


MicroRNAs ( miRNAs ) are important regulators of genes expression. Their levels are precisely controlled through modulating the activity of the microprocesser complex ( MC ) . Here, we report that JANUS, a homology of the conserved U2 snRNP assembly factor in yeast and human, is required for miRNA accumulation. JANUS associates with MC components Dicer-like 1 ( DCL1 ) and SERRATE ( SE ) and directly binds the stem- loop of pri-miRNAs. In a hypomorphic janus mutant, the activity of DCL1, the numbers of MC, and the interaction of primary miRNA transcript ( pri-miRNAs ) with MC are reduced. These data suggest that JANUS promotes the assembly and activity of MC through its interaction with MC and / or pri-miRNAs. In addition, JANUS modulates the transcription of some pri-miRNAs as it binds the promoter of pri-miRNAs and facilitates Pol II occupancy of at their promoters. Moreover, global splicing defects are detected in janus. Taken together, our study reveals a novel role of a conserved splicing factor in miRNA biogenesis.