A KH-domain RNA-binding protein interacts with FIERY2/CTD phosphatase-like 1 and splicing factors and is important for pre-mRNA splicing in Arabidopsis

PLoS Genet. 2013;9(10):e1003875. doi: 10.1371/journal.pgen.1003875. Epub 2013 Oct 17.


Eukaryotic genomes encode hundreds of RNA-binding proteins, yet the functions of most of these proteins are unknown. In a genetic study of stress signal transduction in Arabidopsis, we identified a K homology (KH)-domain RNA-binding protein, HOS5 (High Osmotic Stress Gene Expression 5), as required for stress gene regulation and stress tolerance. HOS5 was found to interact with FIERY2/RNA polymerase II (RNAP II) carboxyl terminal domain (CTD) phosphatase-like 1 (FRY2/CPL1) both in vitro and in vivo. This interaction is mediated by the first double-stranded RNA-binding domain of FRY2/CPL1 and the KH domains of HOS5. Interestingly, both HOS5 and FRY2/CPL1 also interact with two novel serine-arginine (SR)-rich splicing factors, RS40 and RS41, in nuclear speckles. Importantly, FRY2/CPL1 is required for the recruitment of HOS5. In fry2 mutants, HOS5 failed to be localized in nuclear speckles but was found mainly in the nucleoplasm. hos5 mutants were impaired in mRNA export and accumulated a significant amount of mRNA in the nuclei, particularly under salt stress conditions. Arabidopsis mutants of all these genes exhibit similar stress-sensitive phenotypes. RNA-seq analyses of these mutants detected significant intron retention in many stress-related genes under salt stress but not under normal conditions. Our study not only identified several novel regulators of pre-mRNA processing as important for plant stress response but also suggested that, in addition to RNAP II CTD that is a well-recognized platform for the recruitment of mRNA processing factors, FRY2/CPL1 may also recruit specific factors to regulate the co-transcriptional processing of certain transcripts to deal with environmental challenges.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis / genetics*
  • Arabidopsis Proteins / genetics*
  • Arabidopsis Proteins / metabolism
  • Cell Nucleus / genetics
  • Gene Expression Regulation, Plant
  • Mutation
  • Phosphoprotein Phosphatases / genetics*
  • Phosphoprotein Phosphatases / metabolism
  • Protein Binding
  • Protein Structure, Tertiary
  • RNA Precursors / genetics*
  • RNA Splicing / genetics
  • RNA, Double-Stranded / genetics
  • RNA-Binding Proteins / genetics*
  • RNA-Binding Proteins / metabolism
  • Salinity
  • Signal Transduction / genetics
  • Transcription Factors / genetics*
  • Transcription Factors / metabolism
  • Transcription, Genetic*


  • Arabidopsis Proteins
  • RCF3 protein, Arabidopsis
  • RNA Precursors
  • RNA, Double-Stranded
  • RNA-Binding Proteins
  • Transcription Factors
  • CPL1 protein, Arabidopsis
  • Phosphoprotein Phosphatases

Grant support

This study was supported by KAUST Research Funds. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.