The ribonucleotidyl transferase USIP-1 acts with SART3 to promote U6 snRNA recycling

Nucleic Acids Res. 2015 Mar 31;43(6):3344-57. doi: 10.1093/nar/gkv196. Epub 2015 Mar 9.


The spliceosome is a large molecular machine that serves to remove the intervening sequences that are present in most eukaryotic pre-mRNAs. At its core are five small nuclear ribonucleoprotein complexes, the U1, U2, U4, U5 and U6 snRNPs, which undergo dynamic rearrangements during splicing. Their reutilization for subsequent rounds of splicing requires reversion to their original configurations, but little is known about this process. Here, we show that ZK863.4/USIP-1 (U Six snRNA-Interacting Protein-1) is a ribonucleotidyl transferase that promotes accumulation of the Caenorhabditis elegans U6 snRNA. Endogenous USIP-1-U6 snRNA complexes lack the Lsm proteins that constitute the protein core of the U6 snRNP, but contain the U6 snRNP recycling factor SART3/B0035.12. Furthermore, co-immunoprecipitation experiments suggest that SART3 but not USIP-1 occurs also in a separate complex containing both the U4 and U6 snRNPs. Based on this evidence, genetic interaction between usip-1 and sart-3, and the apparent dissociation of Lsm proteins from the U6 snRNA during spliceosome activation, we propose that USIP-1 functions upstream of SART3 to promote U6 snRNA recycling.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Animals, Genetically Modified
  • Caenorhabditis elegans / genetics
  • Caenorhabditis elegans / metabolism
  • Caenorhabditis elegans Proteins / genetics
  • Caenorhabditis elegans Proteins / metabolism*
  • Genes, Helminth
  • Models, Biological
  • Nucleotide Transport Proteins / genetics
  • Nucleotide Transport Proteins / metabolism
  • RNA Interference
  • RNA Nucleotidyltransferases / genetics
  • RNA Nucleotidyltransferases / metabolism
  • RNA Stability
  • RNA, Helminth / genetics
  • RNA, Helminth / metabolism*
  • RNA, Small Nuclear / genetics
  • RNA, Small Nuclear / metabolism*
  • RNA-Binding Proteins / genetics
  • RNA-Binding Proteins / metabolism
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Ribonucleoprotein, U4-U6 Small Nuclear / genetics
  • Ribonucleoprotein, U4-U6 Small Nuclear / metabolism


  • Caenorhabditis elegans Proteins
  • Nucleotide Transport Proteins
  • RNA, Helminth
  • RNA, Small Nuclear
  • RNA-Binding Proteins
  • Recombinant Proteins
  • Ribonucleoprotein, U4-U6 Small Nuclear
  • U6 small nuclear RNA
  • RNA Nucleotidyltransferases