HASTY modulates miRNA biogenesis by linking pri-miRNA transcription and processing

Abstract Post-transcriptional gene silencing mediated by microRNAs (miRNAs) modulates numerous developmental and stress response pathways. For the last two decades, HASTY (HST), ortholog of human EXPORTIN 5, was considered to be a candidate protein that exports plant miRNAs from nucleus cytoplasm. Here, we report HST functions in miRNA pathway independent its cargo-exporting activity Arabidopsis. We found Arabidopsis mutants with impaired shuttling exhibit normal subcellular distribution miRNAs. Interestingly, protein-protein interaction microscopy assays showed directly interacts microprocessor core component DCL1 through N-terminal domain. Moreover, mass spectrometry analysis revealed also interacts independently domain with mediator complex subunit MED37. Further experiments could act as scaffold facilitate recruitment genomic MIRNA loci stabilizing DCL1-MED37 complex, which turn promotes transcription proper processing primary transcripts (pri-miRNAs). Taken together, these results suggest is likely associated formation biogenesis at genes, promoting pri-miRNAs rather than direct export processed nucleus.