Dual roles for the Mss116 cofactor during splicing of the ai5 gamma group II intron

作者：Zingler Nora; Solem Amanda; Pyle Anna Marie^*

来源：Nucleic Acids Research, 2010, 38(19): 6602-6609.

DOI：10.1093/nar/gkq530

The autocatalytic group II intron ai5 gamma from Saccharomyces cerevisiae self-splices under high-salt conditions in vitro, but requires the assistance of the DEAD-box protein Mss116 in vivo and under near-physiological conditions in vitro. Here, we show that Mss116 influences the folding mechanism in several ways. By comparing intron precursor RNAs with long (similar to 300 nt) and short (similar to 20 nt) exons, we observe that long exon sequences are a major obstacle for self-splicing in vitro. Kinetic analysis indicates that Mss116 not only mitigates the inhibitory effects of long exons, but also assists folding of the intron core. Moreover, a mutation in conserved Motif III that impairs unwinding activity (SAT -> AAA) only affects the construct with long exons, suggesting helicase unwinding during exon unfolding, but not in intron folding. Strong parallels between Mss116 and the related protein Cyt-19 from Neurospora crassa suggest that these proteins form a subclass of DEAD-box proteins that possess a versatile repertoire of diverse activities for resolving the folding problems of large RNAs.

• 出版日期2010-10