FgPrp4 Kinase Is Important for Spliceosome B-Complex Activation and Splicing Efficiency in Fusarium graminearum

PLoS Genet. 2016 Apr 8;12(4):e1005973. doi: 10.1371/journal.pgen.1005973. eCollection 2016 Apr.

Abstract

PRP4 encodes the only kinase among the spliceosome components. Although it is an essential gene in the fission yeast and other eukaryotic organisms, the Fgprp4 mutant was viable in the wheat scab fungus Fusarium graminearum. Deletion of FgPRP4 did not block intron splicing but affected intron splicing efficiency in over 60% of the F. graminearum genes. The Fgprp4 mutant had severe growth defects and produced spontaneous suppressors that were recovered in growth rate. Suppressor mutations were identified in the PRP6, PRP31, BRR2, and PRP8 orthologs in nine suppressor strains by sequencing analysis with candidate tri-snRNP component genes. The Q86K mutation in FgMSL1 was identified by whole genome sequencing in suppressor mutant S3. Whereas two of the suppressor mutations in FgBrr2 and FgPrp8 were similar to those characterized in their orthologs in yeasts, suppressor mutations in Prp6 and Prp31 orthologs or FgMSL1 have not been reported. Interestingly, four and two suppressor mutations identified in FgPrp6 and FgPrp31, respectively, all are near the conserved Prp4-phosphorylation sites, suggesting that these mutations may have similar effects with phosphorylation by Prp4 kinase. In FgPrp31, the non-sense mutation at R464 resulted in the truncation of the C-terminal 130 aa region that contains all the conserved Prp4-phosphorylation sites. Deletion analysis showed that the N-terminal 310-aa rich in SR residues plays a critical role in the localization and functions of FgPrp4. We also conducted phosphoproteomics analysis with FgPrp4 and identified S289 as the phosphorylation site that is essential for its functions. These results indicated that FgPrp4 is critical for splicing efficiency but not essential for intron splicing, and FgPrp4 may regulate pre-mRNA splicing by phosphorylation of other components of the tri-snRNP although itself may be activated by phosphorylation at S289.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Enzyme Activation / genetics
  • Fusarium / enzymology
  • Fusarium / genetics*
  • Fusarium / metabolism
  • Protein-Serine-Threonine Kinases / genetics*
  • Protein-Serine-Threonine Kinases / metabolism
  • RNA Splicing / genetics*
  • RNA Splicing Factors
  • Ribonucleoprotein, U4-U6 Small Nuclear / genetics*
  • Ribonucleoprotein, U4-U6 Small Nuclear / metabolism
  • Schizosaccharomyces pombe Proteins / genetics
  • Spliceosomes / genetics*
  • Suppression, Genetic / genetics

Substances

  • RNA Splicing Factors
  • Ribonucleoprotein, U4-U6 Small Nuclear
  • Schizosaccharomyces pombe Proteins
  • Protein-Serine-Threonine Kinases
  • prp4 protein, S pombe

Grant support

This work was supported by grants from the National Major Project of Breeding for New Transgenic Organisms (2012ZX08009003), the Nature Science Foundation of China (No. 31271989; No. 31201464), and US Wheat and Barley Scab Initiative (106616). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.