Two Proteins Essential for Apolipoprotein B mRNA Editing Are Expressed from a Single Gene through Alternative Splicing

Dance, Geoffrey S.C.; Sowden, Mark P.; Cartegni, Luca; Cooper, Ellen M.; Krainer, Adrian R.; Smith, Harold C.

doi:10.1074/jbc.m111337200

Cited by 41 publications

(36 citation statements)

References 40 publications

(44 reference statements)

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“…The C terminus encoded by exon 9␣ included the ligand binding domain, whereas that encoded by exon 9␤ includes a domain that cannot bind GC. Stimulation of alternative splicing for other mRNAs such as fibronectin (34 -36), ␤-tropomyosin (37), apolipoprotein B (apoB) (38), adenylyl cyclase stimulatory Gprotein G ␣(s) (39), and survival motor neuron (40) requires the coordinated action of specific SR proteins and several classes of cis acting mRNA elements including purine-rich splicing enhancers known as exonic splicing elements. These proteins bind and can direct the splicing to alternative splice sites in a concentration-dependent manner, regulate the stability of mRNA, and have a general role in mRNA export (41)(42)(43).…”

Section: Discussionmentioning

confidence: 99%

Serine-Arginine-rich Protein p30 Directs Alternative Splicing of Glucocorticoid Receptor Pre-mRNA to Glucocorticoid Receptor β in Neutrophils

Leung

Kisich

2003

Journal of Biological Chemistry

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Glucocorticoid (GC) insensitivity is a major clinical challenge in the treatment of many inflammatory diseases. It has been shown previously that GC insensitivity, in several inflammatory cell types, is due to an overabundance of the ␤ isoform of the glucocorticoid receptor (GCR␤) relative to the ligand binding isoform, GCR␣. GCR␤ functions as a dominant inhibitor of GCR␣ action. A number of GCR isoforms are created from the same pre-mRNA transcript via alternative splicing, and the factor or factors that control alternative splicing of GCR pre-mRNA are of great importance. In the current study, we have identified the predominant alternative splicing factor present in human neutrophils, which is known to be exceptionally GC-insensitive. The predominant alternative splicing factor in neutrophils is SRp30c, which is one of several highly conserved serinearginine-rich (SR) proteins that are involved in both constitutive and alternative splicing in eukaryotic cells. Inhibition of SRp30c expression with antisense oligonucleotide strongly inhibited expression of GCR␤ and stimulated expression of GCR␣. Antisense molecules targeted to other SR proteins had no effect. Our data indicate that SRp30c is necessary for alternative splicing of the GCR pre-mRNA to create mRNA encoding GCR␤.Glucocorticoid (GC) 1 insensitivity is a major clinical challenge in the treatment of chronic inflammatory diseases. The pharmacologic actions of GCs are mediated through intracellular receptors, the glucocorticoid receptors (GCR). There are two isoforms of GCR in human cells, GCR␣ and GCR␤, which are generated from a single gene via alternative splicing of the primary RNA transcript. Several studies indicate that GC insensitivity has been associated with increased expression of GCR␤ (1-7). GCR␤ is truncated at the C terminus, which corresponds to the ligand binding domain. Thus, GCR␤ cannot bind GC. In addition, GCR␤ does not transactivate GC-sensitive genes and functions as a dominant inhibitor of GCR␣ (8). Previous studies suggest that GCR␣:GCR␤ heterodimer formation may account for the reduced effectiveness of GC action in cells overexpressing GCR␤ (8). Recent experiments in our lab demonstrated that overexpression of human GCR␤ by mouse hybridoma cells results in the development of GC insensitivity by these cells (9).Regulation of GCR␤ expression is not well understood. Different cell types from the same individual can have very different ratios of GCR␣ to GCR␤. For example, freshly isolated peripheral blood neutrophils are GC-insensitive. Both the absolute level of GCR␤ and the ratio of GCR␤ to GCR␣ protein are much higher in neutrophils than in peripheral blood mononuclear cells (PBMC) from the same individuals (10). The ratio of GCR␤ to GCR␣ can be altered by cytokine stimulation. After stimulation of neutrophils with IL-8, GCR␤ mRNA levels increased remarkably, and GCR␣ mRNA decreased to undetectable levels. Similarly, exposure of PBMC to IL-2 and IL-4 resulted in increased GCR␤ expression and development of steroid insensitivity (1,...

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Section: Discussionmentioning

confidence: 99%

Serine-Arginine-rich Protein p30 Directs Alternative Splicing of Glucocorticoid Receptor Pre-mRNA to Glucocorticoid Receptor β in Neutrophils

Leung

Kisich

2003

Journal of Biological Chemistry

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“…1, Table I, and Ref. 23). Each of the splice sites and the polyadenylation signal conformed to their respective consensus motifs (Table I) (43,44).…”

Section: Identification and Molecular Cloning Of Rat Acf45 And Acf43mentioning

confidence: 98%

“…The possibility that acf45 and acf43 mRNAs resulted from alternative splicing of rat acf pre-mRNA was suggested by the recent finding of multiple alternatively spliced variants of human acf pre-mRNA (23,26). To investigate this, the genomic region encompassing exons 11 and 12 (by comparison to the human acf gene structure) was PCR-amplified, subcloned, and sequenced.…”

Section: Identification and Molecular Cloning Of Rat Acf45 And Acf43mentioning

confidence: 99%

“…The acf gene in both human and rats encodes the alternative 5Ј end of exon 12 that is included in the alternative splicing of acf65 mRNA (23,26). However, exon 11A of the rat gene had no similar DNA sequence or amino acid coding potential within the equivalently sized intron 11 of the human gene (23).…”

Section: Identification and Molecular Cloning Of Rat Acf45 And Acf43mentioning

confidence: 99%

“…apoB mRNA editing is catalyzed by a multiprotein complex, or editosome (16,17), that assembles upon an 11-nucleotide mooring sequence positioned 3Ј of the edited cytidine at nucleotide position 6666 (18,19). A minimal editosome assembled in vitro consists of a homodimer of APOBEC-1 (20,21) together with a 64 -65-kDa RNA-binding APOBEC-1 complementation factor (ACF65/ACF64) (22)(23)(24)(25). ACF65 (ASP) or ACF64 (ACF) are expressed through alternative mRNA splicing (23,26) and have equivalent capacity for complementing APOBEC-1 in transfected cells (23).…”

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Identification of Novel Alternative Splice Variants of APOBEC-1 Complementation Factor with Different Capacities to Support Apolipoprotein B mRNA Editing

Sowden

Lehmann

Lin

et al. 2004

Journal of Biological Chemistry

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Two novel mRNA transcripts have been identified that result from species-and tissue-specific, alternative polyadenylation and splicing of the pre-mRNA encoding the apolipoprotein B (apoB) editing catalytic subunit 1 (APOBEC-1) complementation factor (ACF) family of related proteins. The alternatively processed mRNAs encode 43-and 45-kDa proteins that are components of the previously identified p44 cluster of apoB RNA binding, editosomal proteins. Recombinant ACF45 displaced ACF64 and ACF43 in mooring sequence RNA binding but did not demonstrate strong binding to APOBEC-1. In contrast, ACF43 bound strongly to APOBEC-1 but demonstrated weak binding to mooring sequence RNA. Consequently ACF45/43 complemented APOBEC-1 in apoB mRNA editing with less efficiency than full-length ACF64. These data, together with the finding that all ACF variants were co-expressed in rat liver nuclei (the site of apoB mRNA editing), suggested that ACF variants might compete with one another for APOBEC-1 and apoB mRNA binding and thereby contribute to the regulation of apoB mRNA editing. In support for this hypothesis, the ratio of nuclear ACF65/64 to ACF45/43 decreased when hepatic editing was inhibited by fasting and increased when editing was re-stimulated by refeeding. These findings suggested a new model for the regulation of apoB mRNA editing in which the catalytic potential of editosomes is modulated at the level of their assembly by alterations in the relative abundance of multiple related RNA-binding auxiliary proteins and the expression level of APOBEC-1.Alternative mRNA polyadenylation, splicing, and mRNA editing are mechanisms of post-transcriptional RNA processing that introduce diversity in mammalian mRNAs, thereby regulating the number of structurally and functionally different proteins encoded by a single gene (reviewed in Refs. 1 and 2). Base modification RNA editing may involve the enzymatic deamination of single nucleotides within splice site consensus motifs (3) or in protein coding sequence, often with physiologically significant effects (4). Adenosine to inosine editing of mRNAs, such as that occurring on mRNAs encoding the glutamate-gated calcium channel and serotonin 2C receptor subunits, is mediated by a family of adenosine deaminases active on RNAs that function independently of cofactors to deaminate their cognate target within double-stranded RNA (reviewed in Ref. 5). Multiple cytidine deaminases active on RNA have been predicted through their homology with the zinc-dependent cytidine deaminase domain of the mRNA editing enzyme APO-BEC-1 1 (Ref. 6 and references therein); however, only APO-BEC-1 (7, 8) and CDD1 (9) have been shown to deaminate cytidines within mRNA. Unlike adenosine deaminases active on RNA, cytidine deaminases active on RNA minimally require RNA-binding auxiliary proteins for their activity on RNA.Cytidine to uridine deamination of nucleotide 6666 of apolipoprotein B mRNA occurs in the small intestine of all, and the livers of some, mammalian species (10 -12). The glutaminespecifying CAA codon...

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Alternative splicing of HSPA12A pre‐RNA by SRSF11 contributes to metastasis potential of colorectal cancer

Pan

Huo

Kang

et al. 2022

Clinical & Translational Med

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Background Dysregulation of alternative splicing (AS) induced by serine/arginine‐rich proteins has recently been linked to cancer metastasis. Nonetheless, as a member of the serine/arginine‐rich protein family, the involvement of SRSF11 in colorectal cancer (CRC) is unknown. Methods The TCGA dataset and clinical samples were used to assess SRSF11 expression levels in CRC. For SRSF11, functional experiments were conducted both in vitro and in vivo. RNA‐seq technology was used to analyze and screen SRSF11‐triggered AS events, which were then confirmed by in vivo UV crosslinking and immunoprecipitation (CLIP) and mini‐gene reporter assays. Jalview software was used to determine the preferential binding motif with relation to exon skipping (ES) events. Furthermore, coimmunoprecipitation (Co‐IP) and Phospho‐tag SDS‐PAGE experiments were used to investigate PAK5‐mediated phosphorylation regulation on SRSF11, and in vitro kinase experiments validated the interaction. Results In CRC, SRSF11 was discovered to be overexpressed and associated with a poor prognosis. And SRSF11 played a pro‐metastatic role in vitro and in vivo. By screening SRSF11‐regulated AS events, we identified the binding motif of SRSF11‐triggered splicing‐switching of HSPA12A AS, which specifically regulated HSPA12A AS by directly binding to a motif in exon 2. Mechanistically, the HSPA12A transcript with exon 2 retention increased N‐cadherin expression by promoting RNA stability. Furthermore, the oncogenic kinase PAK5 phosphorylated SRSF11 at serine 287, protecting it from ubiquitination degradation. Conclusions SRSF11 exerts pro‐metastatic effects in CRC by inhibiting the AS of HSPA12A pre‐RNA. Our findings point to SRSF11‐regulated HSPA12A splicing as a novel relationship between SRSF11‐regulated splicing and CRC metastasis and suggest a PAK5/SRSF11/HSPA12A axis as a potential therapeutic target and prognostic biomarker in CRC.

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Two Proteins Essential for Apolipoprotein B mRNA Editing Are Expressed from a Single Gene through Alternative Splicing

Cited by 41 publications

References 40 publications

Serine-Arginine-rich Protein p30 Directs Alternative Splicing of Glucocorticoid Receptor Pre-mRNA to Glucocorticoid Receptor β in Neutrophils

Serine-Arginine-rich Protein p30 Directs Alternative Splicing of Glucocorticoid Receptor Pre-mRNA to Glucocorticoid Receptor β in Neutrophils

Identification of Novel Alternative Splice Variants of APOBEC-1 Complementation Factor with Different Capacities to Support Apolipoprotein B mRNA Editing

Alternative splicing of HSPA12A pre‐RNA by SRSF11 contributes to metastasis potential of colorectal cancer

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