Spliceosomal Prp8 intein at the crossroads of protein and RNA splicing

PLoS Biol. 2019 Oct 10;17(10):e3000104. doi: 10.1371/journal.pbio.3000104. eCollection 2019 Oct.


The spliceosome is a large ribonucleoprotein complex that removes introns from pre-mRNAs. At its functional core lies the essential pre-mRNA processing factor 8 (Prp8) protein. Across diverse eukaryotes, this protein cofactor of RNA catalysis harbors a self-splicing element called an intein. Inteins in Prp8 are extremely pervasive and are found at 7 different sites in various species. Here, we focus on the Prp8 intein from Cryptococcus neoformans (Cne), a human fungal pathogen. We solved the crystal structure of this intein, revealing structural homology among protein splicing sequences in eukaryotes, including the Hedgehog C terminus. Working with the Cne Prp8 intein in a reporter assay, we find that the biologically relevant divalent metals copper and zinc inhibit intein splicing, albeit by 2 different mechanisms. Copper likely stimulates reversible modifications on a catalytically important cysteine, whereas zinc binds at the terminal asparagine and the same critical cysteine. Importantly, we also show that copper treatment inhibits Prp8 protein splicing in Cne. Lastly, an intein-containing Prp8 precursor model is presented, suggesting that metal-induced protein splicing inhibition would disturb function of both Prp8 and the spliceosome. These results indicate that Prp8 protein splicing can be modulated, with potential functional implications for the spliceosome.

Publication types

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

MeSH terms

  • Asparagine / chemistry
  • Asparagine / metabolism
  • Binding Sites
  • Cloning, Molecular
  • Copper / chemistry
  • Copper / metabolism
  • Cryptococcus neoformans / genetics*
  • Cryptococcus neoformans / metabolism
  • Crystallography, X-Ray
  • Cysteine / chemistry
  • Cysteine / metabolism
  • Escherichia coli / genetics
  • Escherichia coli / metabolism
  • Fungal Proteins / chemistry
  • Fungal Proteins / genetics*
  • Fungal Proteins / metabolism
  • Gene Expression
  • Genes, Reporter
  • Genetic Vectors / chemistry
  • Genetic Vectors / metabolism
  • Green Fluorescent Proteins / genetics
  • Green Fluorescent Proteins / metabolism
  • Inteins
  • Maltose-Binding Proteins / genetics
  • Maltose-Binding Proteins / metabolism
  • Models, Molecular
  • Protein Binding
  • Protein Conformation, alpha-Helical
  • Protein Conformation, beta-Strand
  • Protein Interaction Domains and Motifs
  • RNA Splicing*
  • RNA-Binding Proteins / chemistry
  • RNA-Binding Proteins / genetics*
  • RNA-Binding Proteins / metabolism
  • Recombinant Fusion Proteins / chemistry
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Sequence Alignment
  • Spliceosomes / metabolism*
  • Spliceosomes / ultrastructure
  • Structural Homology, Protein
  • Zinc / chemistry
  • Zinc / metabolism


  • Fungal Proteins
  • Maltose-Binding Proteins
  • RNA-Binding Proteins
  • Recombinant Fusion Proteins
  • Green Fluorescent Proteins
  • Asparagine
  • Copper
  • Zinc
  • Cysteine