title: Cwc23, an essential J protein critical for pre-mRNA splicing with a dispensable J domain.
abstract: J proteins are structurally diverse, obligatory cochaperones of Hsp70s, each with a highly conserved J domain that plays a critical role in the stimulation of Hsp70's ATPase activity. The essential protein, Cwc23, is one of 13 J proteins found in the cytosol and/or nucleus of Saccharomyces cerevisiae. We report that a partial loss-of-function CWC23 mutant has severe, global defects in pre-mRNA splicing. This mutation leads to accumulation of the excised, lariat form of the intron, as well as unspliced pre-mRNA, suggesting a role for Cwc23 in spliceosome disassembly. Such a role is further supported by the observation that this mutation results in reduced interaction between Cwc23 and Ntr1 (SPP382), a known component of the disassembly pathway. However, Cwc23 is a very atypical J protein. Its J domain, although functional, is dispensable for both cell viability and pre-mRNA splicing. Nevertheless, strong genetic interactions were uncovered between point mutations encoding alterations in Cwc23's J domain and either Ntr1 or Prp43, a DExD/H-box helicase essential for spliceosome disassembly. These genetic interactions suggest that Hsp70-based chaperone machinery does play a role in the disassembly process. Cwc23 provides a unique example of a J protein; its partnership with Hsp70 plays an auxiliary, rather than a central, role in its essential cellular function.
authors.affiliation: Department of Biochemistry, 433 Babcock Dr., University of Wisconsin-Madison, Madison, WI 53706, USA.
authors.forename: Chandan
authors.initials: C
authors.lastname: Sahi
authors.forename: Thomas
authors.initials: T
authors.lastname: Lee
authors.forename: Maki
authors.initials: M
authors.lastname: Inada
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Pleiss
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Craig
mesh_terms: D002470:Cell Survival / Q000502:physiology; D053487:DEAD-box RNA Helicases / Q000502:physiology; D035683:MicroRNAs / Q000502:physiology*; D018832:Molecular Chaperones / Q000235:genetics / Q000502:physiology*; D017354:Point Mutation; D017434:Protein Structure, Tertiary; D012326:RNA Splicing; D012331:RNA, Fungal / Q000502:physiology*; D012333:RNA, Messenger / Q000502:physiology*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000502:physiology*; D017381:Spliceosomes / Q000502:physiology
chemical_list: C546337:Cwc23 protein, S cerevisiae; D035683:MicroRNAs; D018832:Molecular Chaperones; D012331:RNA, Fungal; D012333:RNA, Messenger; D029701:Saccharomyces cerevisiae Proteins; C507652:Spp382 protein, S cerevisiae; C109034:PRP43 protein, S cerevisiae; D053487:DEAD-box RNA Helicases