A minor groove RNA triple helix within the catalytic core of a group I intron

Authors:
  • LOLori Ortoleva-Donnelly
    Lori Ortoleva-Donnelly
  • SRSean P. Ryder
    Sean P. Ryder
  • EMEileen Moncoeur
    Eileen Moncoeur
  • SSScott A. Strobel
    Scott A. Strobel

Abstract
Close packing of several double helical and single stranded RNA elements is required for the Tetrahymena group I ribozyme to achieve catalysis. The chemical basis of these packing interactions is largely unknown. Using nucleotide analog interference suppression (NAIS), we demonstrate that the P1 substrate helix and J8/7 single stranded segment form an extended minor groove triple helix within the catalytic core of the ribozyme. Because each triple in the complex is mediated by at least one 2'-OH group, this substrate recognition triplex is unique to RNA and is fundamentally different from major groove homopurine-homopyrimidine triplexes. We have incorporated these biochemical data into a structural model of the ribozyme core that explains how the J8/7 strand organizes several helices within this complex RNA tertiary structure.