A DEAD-box protein alone promotes group II intron splicing and reverse splicing by acting as an RNA chaperone.
Group II intron RNAs self-splice in vitro but only at high salt and/or Mg2+ concentrations and have been thought to require proteins to stabilize their active structure for efficient splicing in vivo. Here, we show that a DEAD-box protein, CYT-19, can by itself promote the splicing and reverse splicing of the yeast aI5gamma and bI1 group II introns under near-physiological conditions by acting as an ATP-dependent RNA chaperone, whose continued presence is not required after RNA folding. Our results suggest that the folding of some group II introns may be limited by kinetic traps and that their active structures, once formed, do not require proteins or high Mg2+ concentrations for structural stabilization. Thus, during evolution, group II introns could have spliced and transposed by reverse splicing by using ubiquitous RNA chaperones before acquiring more specific protein partners to promote their splicing and mobility. More generally, our results provide additional evidence for the widespread role of RNA chaperones in folding cellular RNAs.
Mohr
Sabine
S
Institute for Cellular and Molecular Biology, Department of Chemistry and Biochemistry and Section of Molecular Genetics and Microbiology, School of Biological Sciences, University of Texas, Austin, TX 78712, USA.
Matsuura
Manabu
M
Perlman
Philip S
PS
Lambowitz
Alan M
AM
D000255:Adenosine Triphosphate / Q000378:metabolism; D001483:Base Sequence; D007438:Introns; D007700:Kinetics; D008274:Magnesium / Q000378:metabolism / Q000494:pharmacology; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism*; D009690:Nucleic Acid Conformation; D020365:RNA Helicases / Q000235:genetics / Q000378:metabolism*; D012326:RNA Splicing; D012331:RNA, Fungal / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012194:RNA-Directed DNA Polymerase / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D012492:Salts / Q000378:metabolism; D013696:Temperature
D018832:Molecular Chaperones; D012331:RNA, Fungal; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; D012492:Salts; D000255:Adenosine Triphosphate; C066564:aI2 protein, S cerevisiae; D012194:RNA-Directed DNA Polymerase; D020365:RNA Helicases; D008274:Magnesium