Nonsense mutations inhibit splicing of MVM RNA in cis when they interrupt the reading frame of either exon of the final spliced product.

Abstract

Missouri 65212 USA mRNAs R1 and R2 of the autonomous parvovirus minute virus of mice (MVM), which encode the viral nonstructural proteins NS1 and NS2, respectively, are processed in an ordered splicing pathway in which R2 is generated from mature spliced R1. Introduction of translation termination signals into these genes alters the processing of these RNAs; there is a significant (up to fourfold) increase in the accumulated steady-state levels of R1 relative to R2, when compared with wild-type levels, although the total accumulated levels of R1 plus R2 remain the same. The increase in accumulated R1 relative to R2 in mutant infected or transfected murine cells is independent of RNA stability and transport and decreases, in a polar manner, with the distance of the inserted termination signal from the shared initiation codon for NS1 and NS2 at nucleotide 260. The increased ratio of R1 to R2 is a consequence of the artificially introduced translation termination signals acting in cis rather than in the absence of a functional viral gene product. These mutations have an effect when they interrupt previously open reading frames in either exon of the spliced product R2. Nonsense mutations that are located in the second exon of R2 inhibit splicing of R1 to R2 only when they interrupt an open reading frame (ORF) that has the potential, after normal splicing, to be joined in-frame with the initiating AUG. These results suggest that nonsense mutations inhibit splicing of R1 to R2 by influencing the mechanism by which exons are defined in murine cells.

A Regulatory Mechanism That Detects Premature Nonsense Codons in T-cell Receptor Transcripts in Vivo Is Reversed by Protein Synthesis Inhibitors in Vitro

“…Our conclusions are consistent with several reports that show that ptcs have no effect on gene transcription in cultured cell lines (8,12,16,19). In contrast, no consensus has emerged regarding the effect of ptcs on pre-mRNA levels in cell lines; ptcs exert no discernible effect on triosephosphate isomerase pre-mRNA levels and thus appear not to affect splicing (19), while ptcs apparently inhibit the splicing of Ig-chain and MVM pre-mRNAs (9,15).…”

Stop codons affect 5′ splice site selection by surveillance of splicing

“…In the fibrillin gene, associated with Marfan syndrome, nonsense, but not missense, mutations were associated with skipping of exon 51 (29). These studies also include cases of intron retention (30)(31)(32)(33)(34). In particular, nonsense mutations in the Ig gene cause defective splicing of this pre-mRNA in a B cell in vitro system (32).…”

A single-base-pair deletion in the beta-glucuronidase gene accounts for the phenotype of murine mucopolysaccharidosis type VII.

“…A recent report showed that skipping of constitutive exons is induced by nonsense mutations (20). In addition, nonsense mutations inhibit splicing of autonomous parvovirus minute virus of mice RNA in cis when they interrupt the reading frame of either exon of the final spliced product (21). Whatever mechanism actually causes the reduced steadystate levels of /-glucuronidase mRNA in mutant mice, the MPS-VII mouse provides an interesting and well-characterized animal model useful for further studies on the relationship between nonsense-codon mutations and mRNA metabolism.…”