title: A DEAD protein that activates intron self-splicing without unwinding RNA.
abstract: The group II intron ai5gamma from S. cerevisiae requires high temperature and salt to self-splice in vitro, but it is assisted by the protein Mss116 in vivo. Here we show that Mss116 can stimulate splicing of ai5gamma under near-physiological conditions in vitro, which represents one of the first cases in which a DExH/D protein is shown to act on its natural target. Importantly, we demonstrate that a small subset of DEAD-box proteins can also stimulate ai5gamma splicing in vitro and may represent a distinct subfamily of DEAD-box proteins that functions in RNA tertiary structure assembly. Mutational analysis shows that while ATPase activity is required for stimulation of splicing by Mss116, helicase activity is not. This finding indicates that Mss116 is unlikely to promote intron splicing through the unwinding of kinetic traps. Rather, we propose that Mss116 promotes the ordered assembly of large RNA molecules through stabilization of on-pathway intermediates.
authors.affiliation: Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520, USA.
authors.forename: Amanda
authors.initials: A
authors.lastname: Solem
authors.forename: Nora
authors.initials: N
authors.lastname: Zingler
authors.forename: Anna Marie
authors.initials: AM
authors.lastname: Pyle
mesh_terms: D001483:Base Sequence; D053487:DEAD-box RNA Helicases / Q000235:genetics / Q000502:physiology*; D007438:Introns / Q000235:genetics / Q000502:physiology*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D012326:RNA Splicing; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000378:metabolism* / Q000502:physiology
chemical_list: D029701:Saccharomyces cerevisiae Proteins; C058150:MSS116 protein, S cerevisiae; D053487:DEAD-box RNA Helicases