期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2010
卷号：107
期号：22
页码：10020-10025
DOI：10.1073/pnas.0906022107
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：To promote fidelity in nuclear pre-mRNA splicing, the spliceosome rejects and discards suboptimal substrates that have engaged the spliceosome. Whereas DExD/H box ATPases have been implicated in rejecting suboptimal substrates, the mechanism for discarding suboptimal substrates has remained obscure. Corroborating evidence that suboptimal, mutated lariat intermediates can be exported to the cytoplasm for turnover, we have found that the ribosome can translate mutated lariat intermediates. By glycerol gradient analysis, we have found that the spliceosome can dissociate mutated lariat intermediates in vivo in a manner that requires the DEAH box ATPase Prp43p. Through an in vitro assay, we demonstrate that Prp43p promotes the discard of suboptimal and optimal 5' exon and lariat intermediates indiscriminately. Finally, we demonstrate a requirement for Prp43p in repressing splicing at a cryptic splice site. We propose a model for the fidelity of exon ligation in which the DEAH box ATPase Prp22p slows the flow of suboptimal intermediates through exon ligation and Prp43p generally promotes discard of intermediates, thereby establishing a pathway for turnover of stalled intermediates. Because Prp43p also promotes spliceosome disassembly after exon ligation, this work establishes a parallel between the discard of suboptimal intermediates and the dissociation of a genuine excised intron product.
