Metal ion catalysis during the exon-ligation step of nuclear pre-mRNA splicing: Extending the parallels between the spliceosome and group II introns

Peter M. Gordon, Erik J. Sontheimer, Joseph A. Piccirilli

Research output: Contribution to journalArticlepeer-review

101 Scopus citations

Abstract

Mechanistic analyses of nuclear pre-mRNA splicing by the spliceosome and group II intron self-splicing provide insight into both the catalytic strategies of splicing and the evolutionary relationships between the different splicing systems. We previously showed that 3'-sulfur substitution at the 3' splice site of a nuclear pre-mRNA has no effect on splicing. We now report that 3'-sulfur substitution at the 3' splice site of a nuclear pre- mRNA causes a switch in metal specificity when the second step of splicing is monitored using a bimolecular exon-ligation assay. This suggests that the spliceosome uses a catalytic metal ion to stabilize the 3'-oxyanion leaving group during the second step of splicing, as shown previously for the first step. The lack of a metal-specificity switch under cis splicing conditions indicates that a rate-limiting conformational change between the two steps of splicing may mask the subsequent chemical step and the metal-specificity switch. As the group II intron, a true ribozyme, uses identical catalytic strategies for splicing, our results strengthen the argument that the spliceosome is an RNA catalyst that shares a common molecular ancestor with group II introns.

Original languageEnglish (US)
Pages (from-to)199-205
Number of pages7
JournalRNA
Volume6
Issue number2
DOIs
StatePublished - Feb 2000

Keywords

  • Evolution
  • Metal-specificity switch
  • Multipartite assay
  • Ribozyme
  • Sulfur substitution

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