title: Role of Cwc24 in the First Catalytic Step of Splicing and Fidelity of 5' Splice Site Selection.
abstract: Cwc24 is an essential splicing factor but only transiently associates with the spliceosome, with an unknown function. The protein contains a RING finger and a zinc finger domain in the carboxyl terminus. The human ortholog of Cwc24, RNF113A, has been associated with the disorder trichothiodystrophy. Here, we show that the zinc finger domain is essential for Cwc24 function, while the RING finger domain is dispensable. Cwc24 binds to the spliceosome after the Prp19-associated complex and is released upon Prp2 action. Cwc24 is not required for Prp2-mediated remodeling of the spliceosome, but the spliceosome becomes inactive if remodeling occurs before the addition of Cwc24. Cwc24 binds directly to pre-mRNA at the 5' splice site, spanning the splice junction. In the absence of Cwc24, U5 and U6 modes of interaction with the 5' splice site are altered, and splicing is very inefficient, with aberrant cleavage at the 5' splice site. Our data suggest roles for Cwc24 in orchestrating organization of the spliceosome into an active configuration prior to Prp2-mediated spliceosome remodeling and in promoting specific interaction of U5 and U6 with the 5' splice site for fidelity of 5' splice site selection.
authors.affiliation: Faculty of Life Sciences and Institute of Genomic Sciences, National Yang-Ming University, Taipei, Taiwan, Republic of China.|Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan, Republic of China.
authors.forename: Nan-Ying
authors.initials: NY
authors.lastname: Wu
authors.affiliation: Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan, Republic of China.
authors.forename: Che-Sheng
authors.initials: CS
authors.lastname: Chung
authors.affiliation: Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan, Republic of China mbscc@ccvax.sinica.edu.tw.
authors.forename: Soo-Chen
authors.initials: SC
authors.lastname: Cheng
mesh_terms: D001483:Base Sequence; D055162:Biocatalysis; D003432:Cross-Linking Reagents / Q000378:metabolism; D011485:Protein Binding; D000072417:Protein Domains; D012322:RNA Precursors / Q000378:metabolism; D022821:RNA Splice Sites / Q000235:genetics*; D012326:RNA Splicing / Q000235:genetics*; D000072260:RNA Splicing Factors / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017381:Spliceosomes / Q000378:metabolism; D013329:Structure-Activity Relationship
chemical_list: D003432:Cross-Linking Reagents; D012322:RNA Precursors; D022821:RNA Splice Sites; D000072260:RNA Splicing Factors; D012333:RNA, Messenger
keywords: Cwc24; Prp2; first catalytic step; spliceosome; splicing fidelity