Flemr M, Schwaiger M, Hess D, Iesmantavicius V, Ahel J, Tuck AC, Mohn F, Bühler M. Mouse nuclear RNAi-defective 2 promotes splicing of weak 5' splice sites.
RNA 2023;
29:1140-1165. [PMID:
37137667 PMCID:
PMC10351895 DOI:
10.1261/rna.079465.122]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2022] [Accepted: 04/19/2023] [Indexed: 05/05/2023]
Abstract
Removal of introns during pre-mRNA splicing, which is central to gene expression, initiates by base pairing of U1 snRNA with a 5' splice site (5'SS). In mammals, many introns contain weak 5'SSs that are not efficiently recognized by the canonical U1 snRNP, suggesting alternative mechanisms exist. Here, we develop a cross-linking immunoprecipitation coupled to a high-throughput sequencing method, BCLIP-seq, to identify NRDE2 (nuclear RNAi-defective 2), and CCDC174 (coiled-coil domain-containing 174) as novel RNA-binding proteins in mouse ES cells that associate with U1 snRNA and 5'SSs. Both proteins bind directly to U1 snRNA independently of canonical U1 snRNP-specific proteins, and they are required for the selection and effective processing of weak 5'SSs. Our results reveal that mammalian cells use noncanonical splicing factors bound directly to U1 snRNA to effectively select suboptimal 5'SS sequences in hundreds of genes, promoting proper splice site choice, and accurate pre-mRNA splicing.
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