KETCH1 imports HYL1 to nucleus for miRNA biogenesis in Arabidopsis

Proc Natl Acad Sci U S A. 2017 Apr 11;114(15):4011-4016. doi: 10.1073/pnas.1619755114. Epub 2017 Mar 27.

Abstract

MicroRNA (miRNA) is processed from primary transcripts with hairpin structures (pri-miRNAs) by microprocessors in the nucleus. How cytoplasmic-borne microprocessor components are transported into the nucleus to fulfill their functions remains poorly understood. Here, we report KETCH1 (karyopherin enabling the transport of the cytoplasmic HYL1) as a partner of hyponastic leaves 1 (HYL1) protein, a core component of microprocessor in Arabidopsis and functional counterpart of DGCR8/Pasha in animals. Null mutation of ketch1 is embryonic-lethal, whereas knockdown mutation of ketch1 caused morphological defects, reminiscent of mutants in the miRNA pathway. ketch1 knockdown mutation also substantially reduced miRNA accumulation, but did not alter nuclear-cytoplasmic shuttling of miRNAs. Rather, the mutation significantly reduced nuclear portion of HYL1 protein and correspondingly compromised the pri-miRNA processing in the nucleus. We propose that KETCH1 transports HYL1 from the cytoplasm to the nucleus to constitute functional microprocessor in Arabidopsis This study provides insight into the largely unknown nuclear-cytoplasmic trafficking process of miRNA biogenesis components through eukaryotes.

Keywords: HYL1; KETCH1; importin β; miRNA; pri-miRNA processing.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Arabidopsis / genetics*
  • Arabidopsis / metabolism
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism*
  • Cell Nucleus / genetics
  • Cell Nucleus / metabolism*
  • Gene Expression Regulation, Plant
  • Karyopherins
  • MicroRNAs / genetics
  • MicroRNAs / metabolism*
  • Mutation
  • Nicotiana / genetics
  • Nicotiana / metabolism
  • Plants, Genetically Modified
  • Protein Transport
  • RNA Processing, Post-Transcriptional
  • RNA-Binding Proteins / genetics
  • RNA-Binding Proteins / metabolism*

Substances

  • Arabidopsis Proteins
  • HYL1 protein, Arabidopsis
  • KETCH1 protein, Arabidopsis
  • Karyopherins
  • MicroRNAs
  • RNA-Binding Proteins