Grc3 programs the essential endoribonuclease Las1 for specific RNA cleavage

Proc Natl Acad Sci U S A. 2017 Jul 11;114(28):E5530-E5538. doi: 10.1073/pnas.1703133114. Epub 2017 Jun 26.


Las1 is a recently discovered endoribonuclease that collaborates with Grc3-Rat1-Rai1 to process precursor ribosomal RNA (rRNA), yet its mechanism of action remains unknown. Disruption of the mammalian Las1 gene has been linked to congenital lethal motor neuron disease and X-linked intellectual disability disorders, thus highlighting the necessity to understand Las1 regulation and function. Here, we report that the essential Las1 endoribonuclease requires its binding partner, the polynucleotide kinase Grc3, for specific C2 cleavage. Our results establish that Grc3 drives Las1 endoribonuclease cleavage to its targeted C2 site both in vitro and in Saccharomyces cerevisiae. Moreover, we observed Las1-dependent activation of the Grc3 kinase activity exclusively toward single-stranded RNA. Together, Las1 and Grc3 assemble into a tetrameric complex that is required for competent rRNA processing. The tetrameric Grc3/Las1 cross talk draws unexpected parallels to endoribonucleases RNaseL and Ire1, and establishes Grc3/Las1 as a unique member of the RNaseL/Ire1 RNA splicing family. Together, our work provides mechanistic insight for the regulation of the Las1 endoribonuclease and identifies the tetrameric Grc3/Las1 complex as a unique example of a protein-guided programmable endoribonuclease.

Keywords: HEPN domain; Las1; endoribonuclease; polynucleotide kinase; pre-rRNA processing.

Publication types

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

MeSH terms

  • Binding Sites
  • Escherichia coli / metabolism
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism*
  • Phosphorylation
  • Polynucleotide 5'-Hydroxyl-Kinase / genetics
  • Polynucleotide 5'-Hydroxyl-Kinase / metabolism*
  • Protein Domains
  • Protein Multimerization
  • RNA Precursors / metabolism
  • RNA Processing, Post-Transcriptional
  • RNA, Ribosomal / analysis
  • Recombinant Proteins / metabolism
  • Ribosomes / metabolism
  • Saccharomyces cerevisiae / enzymology*
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae Proteins / genetics
  • Saccharomyces cerevisiae Proteins / metabolism*
  • Two-Hybrid System Techniques


  • LAS1 protein, S cerevisiae
  • Nuclear Proteins
  • RNA Precursors
  • RNA, Ribosomal
  • Recombinant Proteins
  • Saccharomyces cerevisiae Proteins
  • GRC3 protein, S cerevisiae
  • Polynucleotide 5'-Hydroxyl-Kinase