@article {335,
	title = {Unwinding by local strand separation is critical for the function of DEAD-box proteins as RNA chaperones.},
	journal = {J Mol Biol},
	volume = {389},
	number = {4},
	year = {2009},
	month = {2009 Jun 19},
	pages = {674-93},
	abstract = {The DEAD-box proteins CYT-19 in Neurospora crassa and Mss116p in Saccharomyces cerevisiae are broadly acting RNA chaperones that function in mitochondria to stimulate group I and group II intron splicing and to activate mRNA translation. Previous studies showed that the S. cerevisiae cytosolic/nuclear DEAD-box protein Ded1p could stimulate group II intron splicing in vitro. Here, we show that Ded1p complements mitochondrial translation and group I and group II intron splicing defects in mss116Delta strains, stimulates the in vitro splicing of group I and group II introns, and functions indistinguishably from CYT-19 to resolve different nonnative secondary and/or tertiary structures in the Tetrahymena thermophila large subunit rRNA-DeltaP5abc group I intron. The Escherichia coli DEAD-box protein SrmB also stimulates group I and group II intron splicing in vitro, while the E. coli DEAD-box protein DbpA and the vaccinia virus DExH-box protein NPH-II gave little, if any, group I or group II intron splicing stimulation in vitro or in vivo. The four DEAD-box proteins that stimulate group I and group II intron splicing unwind RNA duplexes by local strand separation and have little or no specificity, as judged by RNA-binding assays and stimulation of their ATPase activity by diverse RNAs. In contrast, DbpA binds group I and group II intron RNAs nonspecifically, but its ATPase activity is activated specifically by a helical segment of E. coli 23S rRNA, and NPH-II unwinds RNAs by directional translocation. The ability of DEAD-box proteins to stimulate group I and group II intron splicing correlates primarily with their RNA-unwinding activity, which, for the protein preparations used here, was greatest for Mss116p, followed by Ded1p, CYT-19, and SrmB. Furthermore, this correlation holds for all group I and group II intron RNAs tested, implying a fundamentally similar mechanism for both types of introns. Our results support the hypothesis that DEAD-box proteins have an inherent ability to function as RNA chaperones by virtue of their distinctive RNA-unwinding mechanism, which enables refolding of localized RNA regions or structures without globally disrupting RNA structure.},
	keywords = {Base Sequence, DEAD-box RNA Helicases, DNA, Mitochondrial, Genetic Complementation Test, Introns, Molecular Chaperones, Molecular Sequence Data, Neurospora crassa, Nucleic Acid Conformation, Protein Biosynthesis, RNA, RNA Splicing, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins},
	issn = {1089-8638},
	doi = {10.1016/j.jmb.2009.04.043},
	author = {Del Campo, Mark and Mohr, Sabine and Jiang, Yue and Jia, Huijue and Jankowsky, Eckhard and Lambowitz, Alan M}
}
