SRSF1 facilitates cytosolic DNA-induced production of type I interferons recognized by RIG-I

Towards understandings of serine/arginine-rich splicing factors

Serine/arginine-rich splicing factors (SRSFs) refer to twelve RNA-binding proteins which regulate splice site recognition and spliceosome assembly during precursor messenger RNA splicing. SRSFs also participate in other RNA metabolic events, such as transcription, translation and nonsense-mediated decay, during their shuttling between nucleus and cytoplasm, making them indispensable for genome diversity and cellular activity. Of note, aberrant SRSF expression and/or mutations elicit fallacies in gene splicing, leading to the generation of pathogenic gene and protein isoforms, which highlights the therapeutic potential of targeting SRSF to treat diseases. In this review, we updated current understanding of SRSF structures and functions in RNA metabolism. Next, we analyzed SRSF-induced aberrant gene expression and their pathogenic outcomes in cancers and non-tumor diseases. The development of some well-characterized SRSF inhibitors was discussed in detail. We hope this review will contribute to future studies of SRSF functions and drug development targeting SRSFs.

Serine and arginine rich splicing factor 1: a potential target for neuroprotection and other diseases

Alternative splicing is the process of producing variably spliced mRNAs by choosing distinct combinations of splice sites within a messenger RNA precursor. This splicing enables mRNA from a single gene to synthesize different proteins, which have different cellular properties and functions and yet arise from the same single gene. A family of splicing factors, Serine-arginine rich proteins, are needed to initiate the assembly and activation of the spliceosome. Serine and arginine rich splicing factor 1, part of the arginine/serine-rich splicing factor protein family, can either activate or inhibit the splicing of mRNAs, depending on the phosphorylation status of the protein and its interaction partners. Considering that serine and arginine rich splicing factor 1 is either an activator or an inhibitor, this protein has been studied widely to identify its various roles in different diseases. Research has found that serine and arginine rich splicing factor 1 is a key target for neuroprotection, showing its promising potential use in therapeutics for neurodegenerative disorders. Furthermore, serine and arginine rich splicing factor 1 might be used to regulate cancer development and autoimmune diseases. In this review, we highlight how serine and arginine rich splicing factor 1 has been studied concerning neuroprotection. In addition, we draw attention to how serine and arginine rich splicing factor 1 is being studied in cancer and immunological disorders, as well as how serine and arginine rich splicing factor 1 acts outside the central or peripheral nervous system.

Adaptive homeostasis and the p53 isoform network

All living organisms have developed processes to sense and address environmental changes to maintain a stable internal state (homeostasis). When activated, the p53 tumour suppressor maintains cell and organ integrity and functions in response to homeostasis disruptors (stresses) such as infection, metabolic alterations and cellular damage. Thus, p53 plays a fundamental physiological role in maintaining organismal homeostasis. The TP53 gene encodes a network of proteins (p53 isoforms) with similar and distinct biochemical functions. The p53 network carries out multiple biological activities enabling cooperation between individual cells required for long‐term survival of multicellular organisms (animals) in response to an ever‐changing environment caused by mutation, infection, metabolic alteration or damage. In this review, we suggest that the p53 network has evolved as an adaptive response to pathogen infections and other environmental selection pressures.

Genome-wide transcriptome analysis identifies alternative splicing regulatory network and key splicing factors in mouse and human psoriasis

Psoriasis is a chronic inflammatory disease that affects the skin, nails, and joints. For understanding the mechanism of psoriasis, though, alternative splicing analysis has received relatively little attention in the field. Here, we developed and applied several computational analysis methods to study psoriasis. Using psoriasis mouse and human datasets, our differential alternative splicing analyses detected hundreds of differential alternative splicing changes. Our analysis of conservation revealed many exon-skipping events conserved between mice and humans. In addition, our splicing signature comparison analysis using the psoriasis datasets and our curated splicing factor perturbation RNA-Seq database, SFMetaDB, identified nine candidate splicing factors that may be important in regulating splicing in the psoriasis mouse model dataset. Three of the nine splicing factors were confirmed upon analyzing the human data. Our computational methods have generated predictions for the potential role of splicing in psoriasis. Future experiments on the novel candidates predicted by our computational analysis are expected to provide a better understanding of the molecular mechanism of psoriasis and to pave the way for new therapeutic treatments.

Expression Profile of Three Splicing Factors in Pleural Cells Based on the Underlying Etiology and Its Clinical Values in Patients with Pleural Effusion

Splicing factors (SFs) are involved in oncogenesis or immune modulation, the common underlying processes giving rise to pleural effusion (PE). The expression profiles of three SFs (HNRNPA1, SRSF1, and SRSF3) and their clinical values have never been assessed in PE. The three SFs (in pellets of PE) and conventional tumor markers were analyzed using PE samples in patients with PE (N = 336). The sum of higher-molecular weight (Mw) forms of HNRNPA1 (Sum-HMws-HNRNPA1) and SRSF1 (Sum-HMws-SRSF1) and SRSF3 levels were upregulated in malignant PE (MPE) compared to benign PE (BPE); they were highest in cytology-positive MPE, followed by tuberculous PE and parapneumonic PE. Meanwhile, the lowest-Mw HNRNPA1 (LMw-HNRNPA1) and SRSF1 (LMw-SRSF1) levels were not upregulated in MPE. Sum-HMws-HNRNPA1, Sum-HMws-SRSF1, and SRSF3, but neither LMw-HNRNPA1 nor LMw-SRSF1, showed positive correlations with cancer cell percentages in MPE. The detection accuracy for MPE was high in the order of carcinoembryonic antigen (CEA, 85%), Sum-HMws-HNRNPA1 (76%), Sum-HMws-SRSF1 (68%), SRSF3, cytokeratin-19 fragments (CYFRA 21-1), LMw-HNRNPA1, and LMw-SRSF1. Sum-HMws-HNRNPA1 detected more than half of the MPE cases that were undetected by cytology and CEA. Sum-HMws-HNRNPA1, but not other SFs or conventional tumor markers, showed an association with longer overall survival among patients with MPE receiving chemotherapy. Our results demonstrated different levels of the three SFs with their Mw-specific profiles depending on the etiology of PE. We suggest that Sum-HMws-HNRNPA1 is a supplementary diagnostic marker for MPE and a favorable prognostic indicator for patients with MPE receiving chemotherapy.

A Cytoplasmic RNA Virus Alters the Function of the Cell Splicing Protein SRSF2

To replicate efficiently, viruses must create favorable cell conditions and overcome cell antiviral responses. We previously reported that the reovirus protein μ2 from strain T1L, but not strain T3D, represses one antiviral response: alpha/beta interferon signaling. We report here that T1L, but not T3D, μ2 localizes to nuclear speckles, where it forms a complex with the mRNA splicing factor SRSF2 and alters its subnuclear localization. Reovirus replicates in cytoplasmic viral factories, and there is no evidence that reovirus genomic or messenger RNAs are spliced, suggesting that T1L μ2 might target splicing of cell RNAs. Indeed, RNA sequencing revealed that reovirus T1L, but not T3D, infection alters the splicing of transcripts for host genes involved in mRNA posttranscriptional modifications. Moreover, depletion of SRSF2 enhanced reovirus replication and cytopathic effect, suggesting that T1L μ2 modulation of splicing benefits the virus. This provides the first report of viral antagonism of the splicing factor SRSF2 and identifies the viral protein that determines strain-specific differences in cell RNA splicing.IMPORTANCE Efficient viral replication requires that the virus create favorable cell conditions. Many viruses accomplish this by repressing specific antiviral responses. We demonstrate here that some mammalian reoviruses, RNA viruses that replicate strictly in the cytoplasm, express a protein variant that localizes to nuclear speckles, where it targets a cell mRNA splicing factor. Infection with a reovirus strain that targets this splicing factor alters splicing of cell mRNAs involved in the maturation of many other cell mRNAs. Depletion of this cell splicing factor enhances reovirus replication and cytopathic effect. Our results provide the first evidence of viral antagonism of this splicing factor and suggest that downstream consequences to the cell are global and benefit the virus.

The immunogenetics of Psoriasis: A comprehensive review

Psoriasis vulgaris is a common, chronic inflammatory skin disease with a complex etiology involving genetic risk factors and environmental triggers. Here we describe the many known genetic predispositions of psoriasis with respect to immune genes and their encoded pathways in psoriasis susceptibility. These genes span an array of functions that involve antigen presentation (HLA-Cw6, ERAP1, ERAP2, MICA), the IL-23 axis (IL12Bp40, IL23Ap19, IL23R, JAK2, TYK2), T-cell development and T-cells polarization (RUNX1, RUNX3, STAT3, TAGAP, IL4, IL13), innate immunity (CARD14, c-REL, TRAF3IP2, DDX58, IFIH1), and negative regulators of immune responses (TNIP1, TNFAIP3, NFKBIA, ZC3H12C, IL36RN, SOCS1). The contribution of some of these gene products to psoriatic disease has also been revealed in recent years through targeting of key immune components, such as the Th17/IL-23 axis which has been highly successful in disease treatment. However, many of the genetic findings involve immune genes with less clear roles in psoriasis pathogenesis. This is particularly the case for those genes involved in innate immunity and negative regulation of immune specific pathways. It is possible that risk alleles of these genes decrease the threshold for the initial activation of the innate immune response. This could then lead to the onslaught of the pathogenic adaptive immune response known to be active in psoriatic skin. However, precisely how these various genes affect immunobiology need to be determined and some are speculated upon in this review. These novel genetic findings also open opportunities to explore novel therapeutic targets and potentially the development of personalized medicine, as well as discover new biology of human skin disease.