Upstream analysis of alternative splicing: a review of computational approaches to predict context-dependent splicing factors.

Alternative splicing (AS) has shown to play a pivotal role in the development of diseases, including cancer. Specifically, all the hallmarks of cancer (angiogenesis, cell immortality, avoiding immune system response, etc.) are found to have a counterpart in aberrant splicing of key genes. Identifying the context-specific regulators of splicing provides valuable information to find new biomarkers, as well as to define alternative therapeutic strategies. The computational models to identify these regulators are not trivial and require three conceptual steps: the detection of AS events, the identification of splicing factors that potentially regulate these events and the contextualization of these pieces of information for a specific experiment. In this work, we review the different algorithmic methodologies developed for each of these tasks. Main weaknesses and strengths of the different steps of the pipeline are discussed. Finally, a case study is detailed to help the reader be aware of the potential and limitations of this computational approach.

Modulation of SRSF2 expression reverses the exhaustion of TILs via the epigenetic regulation of immune checkpoint molecules.

The elevated expression of immune checkpoints by the tumor microenvironment is associated with poor prognosis in several cancers due to the exhaustion of tumor-infiltrating lymphocytes (TILs), and the effective suppression of the expression of these genes is key to reversing the exhaustion of TILs. Herein, we determined that serine/arginine-rich splicing factor 2 (SRSF2) is a target for blocking the tumor microenvironment-associated immunosuppressive effects. We found that the expression of SRSF2 was increased in exhausted T cells and that SRSF2 was involved in multiple immune checkpoint molecules mediating TILs' exhaustion. Furthermore, SRSF2 was revealed to regulate the transcription of these immune checkpoint genes by associating with an acyl-transferases P300/CBP complex and altering the H3K27Ac level near these genes, thereafter influencing the recruitment of signal transducer and activator of transcription 3 (STAT3) to these gene promoters. Collectively, our data indicated that SRSF2 functions as a modulator of the anti-tumor response of T cells and may be a therapeutic target for reversing the exhaustion of TILs.

Aberrant splicing in B-cell acute lymphoblastic leukemia.

Aberrant splicing is a hallmark of leukemias with mutations in splicing factor (SF)-encoding genes. Here we investigated its prevalence in pediatric B-cell acute lymphoblastic leukemias (B-ALL), where SFs are not mutated. By comparing these samples to normal pro-B cells, we found thousands of aberrant local splice variations (LSVs) per sample, with 279 LSVs in 241 genes present in every comparison. These genes were enriched in RNA processing pathways and encoded ∼100 SFs, e.g. hnRNPA1. HNRNPA1 3'UTR was most pervasively mis-spliced, yielding the transcript subject to nonsense-mediated decay. To mimic this event, we knocked it down in B-lymphoblastoid cells and identified 213 hnRNPA1-regulated exon usage events comprising the hnRNPA1 splicing signature in pediatric leukemia. Some of its elements were LSVs in DICER1 and NT5C2, known cancer drivers. We searched for LSVs in other leukemia and lymphoma drivers and discovered 81 LSVs in 41 additional genes. Seventy-seven LSVs out of 81 were confirmed using two large independent B-ALL RNA-seq datasets, and the twenty most common B-ALL drivers, including NT5C2, showed higher prevalence of aberrant splicing than of somatic mutations. Thus, post-transcriptional deregulation of SF can drive widespread changes in B-ALL splicing and likely contributes to disease pathogenesis.

A SRSF1 self-binding mechanism restrains Mir505-3p from inhibiting proliferation of neural tumor cell lines.

Srsf1 has currently been demonstrated to be an oncogene that is precisely autoregulated for normal physiology. Although Mir505-3p has been reported as one of the regulatory miRNAs of Srsf1 in mouse embryonic fibroblast (MEF), the inhibitory effect of Mir505-3p on Srsf1 is poorly described in neural tumors. Whether SRSF1 autoregulation interferes with miRNA targeting on the Srsf1 transcript is unclear. In this work, we screened out one target site, out of three potential target sites on 3' UTR of Srsf1 transcript, that was required for Mir505-3p targeting. We showed that Mir505-3p was capable of inhibiting tumor proliferation driven by SRSF1 in two neural tumor cell lines, Neuro-2a (N2a) and U251, exclusively in serum-reduced condition. We observed that the protein level of SRSF1 was gradually promoted by increasing concentration of serum. We also found that overexpressed exogenous SRSF1 protein abolished this RNA interfering related targeting, suggesting that serum-rich condition restrains Mir505-3p from inhibiting Srsf1 transcript after inducing SRSF1 protein overexpression. Moreover, by applying bioinformatic analysis, the SRSF1 self-binding motif was found proximal to the Mir505-3p target site, which was required for a SRSF1 competitive self-binding interaction. The interaction of overexpressed exogenous SRSF1 protein and the SRSF1 self-binding motif was sufficient to restrain Mir505-3p from targeting the Srsf1 transcript. These results provide a better understanding of how tumorous microenvironment influences anticancer therapy in the neural system, suggesting potential strategic design for anticancer drugs.

LncRNA MALAT1 is dysregulated in diabetic nephropathy and involved in high glucose-induced podocyte injury via its interplay with ß-catenin.

Metastasis associated lung adenocarcinoma transcript 1(MALAT1) is a long non-coding RNA, broadly expressed in mammalian tissues including kidney and up-regulated in a variety of cancer cells. To date, its functions in podocytes are largely unknown. ß-catenin is a key mediator in the canonical and non-canonical Wnt signalling pathway; its aberrant expression promotes podocyte malfunction and albuminuria, and contributes to kidney fibrosis. In this study, we found that MALAT1 levels were increased in kidney cortices from C57BL/6 mice with streptozocin (STZ)-induced diabetic nephropathy, and dynamically regulated in cultured mouse podocytes stimulated with high glucose, which showed a trend from rise to decline. The decline of MALAT1 levels was accompanied with ß-catenin translocation to the nuclei and enhanced expression of serine/arginine splicing factor 1 (SRSF1), a MALAT1 RNA-binding protein. Further we showed early interference with MALAT1 siRNA partially restored podocytes function and prohibited ß-catenin nuclear accumulation and SRSF1 overexpression. Intriguingly, we showed that ß-catenin was involved in MALAT1 transcription by binding to the promotor region of MALAT1; ß-catenin knock-down also decreased MALAT1 levels, suggesting a novel feedback regulation between MALAT1 and ß-catenin. Notably, ß-catenin deletion had limited effects on SRSF1 expression, demonstrating ß-catenin might serve as a downstream signal of SRSF1. These findings provided evidence for a pivotal role of MALAT1 in diabetic nephropathy and high glucose-induced podocyte damage.

Immune suppression of JC virus gene expression is mediated by SRSF1.

Progressive multifocal leukoemcephalopathy (PML) is a fatal demyelinating disease caused by the human neurotropic JC virus (JCV). JCV infects the majority of the human population during childhood and establishes a latent/persistent life-long infection. The virus reactivates under immunosuppressive conditions by unknown mechanisms, resulting in productive infection of oligodendrocytes in the central nervous system (CNS). Given the fact that the natural occurrence of PML is strongly associated with immunosuppression, the functional and molecular interaction between glial cells and neuroimmune signaling mediated by soluble immune mediators is likely to play a major role in reactivation of JCV and the progression of the lytic viral life cycle leading to the development of PML. In order to explore the effect of soluble immune mediators secreted by peripheral blood mononuclear cells (PBMCs) on JCV transcription, primary human fetal glial (PHFG) cells were treated with conditioned media from PBMCs. We observed a strong suppression of JCV early as well as late gene transcription in cells treated with conditioned media from induced PBMCs. Using a variety of virological and molecular biological approaches, we demonstrate that immune mediators secreted by PBMCs induce the expression of SRSF1, a strong inhibitor of JCV gene expression, and inhibit the replication of JCV. Our results show that downregulation of SRSF1 in glial cells overcomes the suppression of JCV gene expression and its replication mediated by soluble immune mediators. These findings suggest the presence of a novel immune signaling pathway between glial cells and PBMCs that may control JCV gene expression during the course of viral reactivation.

Omi inhibition ameliorates neuron apoptosis and neurological deficit after subarachnoid hemorrhage in rats.

BACKGROUND: Subarachnoid hemorrhage (SAH) is a severe neurological emergency, resulting in cognitive impairments and threatening human's health. Currently, SAH has no effective treatment. It is urgent to search for an effective therapy for SAH. OBJECTIVE: To explore the expression of Omi protein after subarachnoid hemorrhage in rats. METHODS: SAH rat model was established by injecting blood into the prechiasmatic cistern. Neurological deficit was assessed by detecting neurological deficit scores and brain tissue water contents. Apoptotic cells were evaluated by TUNEL staining and IHC staining. Omi and Cleaved caspase 3 expressions in nerve cells were determined by double staining using IF. Apoptosis-related proteins were measured by Western blotting assay. RESULTS: SAH rat model was successfully established, showing more apoptotic cells and high neurological deficit scores in SAH rat. In SAH rat model, Omi expression in nerve cells was elevated and the upregulation of Omi mainly occurred in cytoplasm, accompanied by the degradation of XIAP and the increased cleaved caspase 3/9 and cleaved PARP. Once treated with UCF-101, a specific inhibitor of Omi, the increased cell apoptosis, left/right brain moisture contents and neurological deficits were notably reversed in SAH rat brain. Of note, SAH-induced the increases of apoptosis-related protein in nerve cells were also rescued by the administration of UCF-101. CONCLUSIONS: UCF-101-mediated Omi inhibition decreased the degradation of XIAP and subsequently inhibited the activation of apoptosis-related proteins, decreased nerve cell apoptosis, leading to the improvement on early brain injury in SAH rat. UCF-101-based Omi inhibition may be used to treat SAH with great potential application.

Inhibition of SRSF9 enhances the sensitivity of colorectal cancer to erastin-induced ferroptosis by reducing glutathione peroxidase 4 expression.

Ferroptosis, a newly iron-dependent form of cell death, is often accompanied by the damage of membrane lipid peroxide. Recently, the ferroptosis inducer erastin has been reported to exhibit potential anti-cancer activities. The aim of this study was to investigate the effects of SRSF9 on the sensitivity of colorectal cancer (CRC) to erastin and explore the underlying molecular mechanism. Short hairpin RNAs (shRNAs) or SRSF9 overexpression vector (SRSF9-OE) was transfected into erastin-induced human CRC cells to inhibit or overexpress SRSF9. Results showed that SRSF9 inhibition promoted the cell death induced by erastin, conversely, SRSF9 overexpression augmented the resistance to erastin-induced death in human CRC cells. SRSF9 decreased lipid peroxide damage which was a key event during erastin-induced ferroptosis in human CRC cells. Furthermore, we found that SRSF9 inhibition increased erastin-induced ferroptosis by downregulating GPX4 level. In an In vivo study, SRSF9 shRNA or SRSF9-OE stably transfected human CRC cells were subcutaneously injected into the right flank of nude mice. SRSF9 overexpression partly abolished the tumor growth inhibition and ferroptosis induced by erastin. Our data indicated SRSF9's regulation of GPX4 as an essential mechanism driving CRC tumorigenesis and resistance of erastin-induced ferroptosis. This molecular mechanism may provide a novel method for improving the sensitivity of CRC to erastin.

Targeting Alternative Splicing for Reversal of Cellular Senescence in the Context of Aesthetic Aging.

SUMMARY: Cellular senescence is a state of stable cell cycle arrest that has increasingly been linked with cellular, tissue, and organismal aging; targeted removal of senescent cells brings healthspan and lifespan benefits in animal models. Newly emerging approaches to specifically ablate or rejuvenate senescent cells are now the subject of intense study to explore their utility to provide novel treatments for the aesthetic signs and diseases of aging in humans. Here, we discuss different strategies that are being trialed in vitro, and more recently in vivo, for the targeted removal or reversal of senescent cells. Finally, we describe the evidence for a newly emerging molecular mechanism that may underpin senescence; dysregulation of alternative splicing. We will explore the potential of restoring splicing regulation as a novel "senotherapeutic" approach and discuss strategies by which this could be integrated into the established portfolio of skin aging therapeutics.

Eucalyptal A inhibits glioma by rectifying oncogenic splicing of MYO1B mRNA via suppressing SRSF1 expression.

Glioma is the most common primary intracranial tumor, in which glioblastoma (GBM) is the most malignant and lethal. However, the current chemotherapy drugs are still unsatisfactory for GBM therapy. As the natural products mainly extracted from Eucalyptus species, phloroglucinol-terpene adducts have the potential to be anti-cancer lead compounds that attracted increasing attention. In order to discover the new lead compounds with the anti-GBM ability, we isolated Eucalyptal A with a phloroglucinol-terpene skeleton from the fruit of E. globulus and investigated its anti-GBM activity in vitro and in vivo. Functionally, we verified that Eucalyptal A could inhibit the proliferation, growth and invasiveness of GBM cells in vitro. Moreover, Eucalyptal A had the same anti-GBM activity in tumor-bearing mice as in vitro and prolonged the overall survival time by maintaining mice body weight. Further mechanism research revealed that Eucalyptal A downregulated SRSF1 expression and rectified SRSF1-guided abnormal alternative splicing of MYO1B mRNA, which led to anti-GBM activity through the PDK1/AKT/c-Myc and PAK/Cofilin axes. Taken together, we identified Eucalyptal A as an important anti-GBM lead compound, which represents a novel direction for glioma therapy.

Inhibition of HtrA2 alleviates inflammatory response and cell apoptosis in lipopolysaccharide­induced acute pneumonia in rats.

Pneumonia is one of the commonest causes of death worldwide. High­temperature requirement A2 (HtrA2) is a proapoptotic mitochondrial serine protease involved in caspase­dependent or caspase­independent cell apoptosis. UCF­101 (5­[5­(2­nitrophenyl) furfuryl iodine]­1,3­diphenyl­2­thiobarbituric acid), an inhibitor of HtrA2, has a protective effect on organs in various diseases by inhibiting cell apoptosis. The aim of the present study was to explore whether UCF­101 has a protective effect on lungs in pneumonia. A lipopolysaccharide (LPS)­induced pneumonia model was established in rats. UCF­101 (2 µmol/kg) was used for treatment. Lung injury was detected by hematoxylin and eosin staining. Pro­inflammatory cytokines and oxidative stress­related factors were detected using corresponding test kits. TUNEL staining was used to measure the amount of cell apoptosis. Apoptosis­associated proteins were detected by western blot assay. The present study indicated pulmonary injury induced by LPS. Treatment with UCF­101 clearly alleviated this pulmonary damage and restored the levels of pro­inflammatory cytokines and oxidative stress­related factors. In addition, UCF­101 significantly reduced LPS­induced cell apoptosis, the release of HtrA2 and cytochrome from mitochondria to the cytoplasm and inhibited the expression of pro­apoptotic proteins. UCF­101 also restored the ATP level. The present results demonstrated that UCF­101 acts as a positive regulator of acute pneumonia by inhibiting inflammatory response, oxidative stress and mitochondrial apoptosis. The present study suggests UCF­101 as a potential candidate for pneumonia therapy.

Specific inhibition of splicing factor activity by decoy RNA oligonucleotides.

Alternative splicing, a fundamental step in gene expression, is deregulated in many diseases. Splicing factors (SFs), which regulate this process, are up- or down regulated or mutated in several diseases including cancer. To date, there are no inhibitors that directly inhibit the activity of SFs. We designed decoy oligonucleotides, composed of several repeats of a RNA motif, which is recognized by a single SF. Here we show that decoy oligonucleotides targeting splicing factors RBFOX1/2, SRSF1 and PTBP1, can specifically bind to their respective SFs and inhibit their splicing and biological activities both in vitro and in vivo. These decoy oligonucleotides present an approach to specifically downregulate SF activity in conditions where SFs are either up-regulated or hyperactive.

SRSF3-Regulated RNA Alternative Splicing Promotes Glioblastoma Tumorigenicity by Affecting Multiple Cellular Processes.

Misregulated alternative RNA splicing (AS) contributes to the tumorigenesis and progression of human cancers, including glioblastoma (GBM). Here, we showed that a major splicing factor, serine and arginine rich splicing factor 3 (SRSF3), was frequently upregulated in clinical glioma specimens and that elevated SRSF3 was associated with tumor progression and a poor prognosis for patients with glioma. In patient-derived glioma stem-like cells (GSC), SRSF3 expression promoted cell proliferation, self-renewal, and tumorigenesis. Transcriptomic profiling identified more than 1,000 SRSF3-affected AS events, with a preference for exon skipping in genes involved with cell mitosis. Motif analysis identified the sequence of CA(G/C/A)CC(C/A) as a potential exonic splicing enhancer for these SRSF3-regulated exons. To evaluate the biological impact of SRSF3-affected AS events, four candidates were selected whose AS correlated with SRSF3 expression in glioma tissues, and their splicing pattern was modified using a CRISPR/Cas9 approach. Two functionally validated AS candidates were further investigated for the mechanisms underlying their isoform-specific functions. Specifically, following knockout of SRSF3, transcription factor ETS variant 1 (ETV1) gene showed exon skipping at exon 7, while nudE neurodevelopment protein 1 (NDE1) gene showed replacement of terminal exon 9 with a mutually exclusive exon 9'. SRSF3-regulated AS of these two genes markedly increased their oncogenic activity in GSCs. Taken together, our data demonstrate that SRSF3 is a key regulator of AS in GBM and that understanding mechanisms of misregulated AS could provide critical insights for developing effective therapeutic strategies against GBMs. SIGNIFICANCE: SRSF3 is a significant regulator of glioma-associated alternative splicing, implicating SRSF3 as an oncogenic factor that contributes to the tumor biology of GBM.

SRp55 Regulates a Splicing Network That Controls Human Pancreatic ß-Cell Function and Survival.

Progressive failure of insulin-producing ß-cells is the central event leading to diabetes, but the signaling networks controlling ß-cell fate remain poorly understood. Here we show that SRp55, a splicing factor regulated by the diabetes susceptibility gene GLIS3, has a major role in maintaining the function and survival of human ß-cells. RNA sequencing analysis revealed that SRp55 regulates the splicing of genes involved in cell survival and death, insulin secretion, and c-Jun N-terminal kinase (JNK) signaling. In particular, SRp55-mediated splicing changes modulate the function of the proapoptotic proteins BIM and BAX, JNK signaling, and endoplasmic reticulum stress, explaining why SRp55 depletion triggers ß-cell apoptosis. Furthermore, SRp55 depletion inhibits ß-cell mitochondrial function, explaining the observed decrease in insulin release. These data unveil a novel layer of regulation of human ß-cell function and survival, namely alternative splicing modulated by key splicing regulators such as SRp55, that may cross talk with candidate genes for diabetes.

Splicing factor gene mutations in the myelodysplastic syndromes: impact on disease phenotype and therapeutic applications.

Splicing factor gene mutations are the most frequent mutations found in patients with the myeloid malignancy myelodysplastic syndrome (MDS), suggesting that spliceosomal dysfunction plays a major role in disease pathogenesis. The aberrantly spliced target genes and deregulated cellular pathways associated with the commonly mutated splicing factor genes in MDS (SF3B1, SRSF2 and U2AF1) are being identified, illuminating the molecular mechanisms underlying MDS. Emerging data from mouse modeling studies indicate that the presence of splicing factor gene mutations can lead to bone marrow hematopoietic stem/myeloid progenitor cell expansion, impaired hematopoiesis and dysplastic differentiation that are hallmarks of MDS. Importantly, recent evidence suggests that spliceosome inhibitors and splicing modulators may have therapeutic value in the treatment of splicing factor mutant myeloid malignancies.

SR proteins regulate V6 exon splicing of CD44 pre-mRNA.

CD44 pre-mRNA includes 20 exons, of which exons 1-5 (C1-C5) and exons 16-20 (C6-C10) are constant exons, whereas exons 6-15 (V1-V10) are variant exons. V6-exon-containing isoforms have been known to be implicated in tumor cell invasion and metastasis. In the present study, we performed a SR protein screen for CD44 V6 splicing using overexpression and lentivirus-mediated shRNA treatment. Using a CD44 V6 minigene, we demonstrate that increased SRSF3 and SRSF4 expression do not affect V6 splicing, but increased expression of SRSF1, SRSF6 and SRSF9 significantly inhibit V6 splicing. In addition, using a constitutive exon-specific primer set, we could not detect alterations of CD44 splicing after SR protein-targeting shRNA treatment. However, using a V6 specific primer, we identified that reduced SRSF2 expression significantly reduced the V6 isoform, but increased V6-10 and V6,7-10 isoforms. Our results indicate that SR proteins are important regulatory proteins for CD44 V6 splicing. [BMB Reports 2016; 49(11): 612-616].

The High Level of Aberrant Splicing of ISCU in Slow-Twitch Muscle May Involve the Splicing Factor SRSF3.

Hereditary myopathy with lactic acidosis (HML) is an autosomal recessive disease caused by an intronic one-base mutation in the iron-sulfur cluster assembly (ISCU) gene, resulting in aberrant splicing. The incorrectly spliced transcripts contain a 100 or 86 bp intron sequence encoding a non-functional ISCU protein, which leads to defects in several Fe-S containing proteins in the respiratory chain and the TCA cycle. The symptoms in HML are restricted to skeletal muscle, and it has been proposed that this effect is due to higher levels of incorrectly spliced ISCU in skeletal muscle compared with other energy-demanding tissues. In this study, we confirm that skeletal muscle contains the highest levels of incorrect ISCU splice variants compared with heart, brain, liver and kidney using a transgenic mouse model expressing human HML mutated ISCU. We also show that incorrect splicing occurs to a significantly higher extent in the slow-twitch soleus muscle compared with the gastrocnemius and quadriceps. The splicing factor serine/arginine-rich splicing factor 3 (SRSF3) was identified as a potential candidate for the slow fiber specific regulation of ISCU splicing since this factor was expressed at higher levels in the soleus compared to the gastrocnemius and quadriceps. We identified an interaction between SRSF3 and the ISCU transcript, and by overexpressing SRSF3 in human myoblasts we observed increased levels of incorrectly spliced ISCU, while knockdown of SRSF3 resulted in decreased levels. We therefore suggest that SRSF3 may participate in the regulation of the incorrect splicing of mutant ISCU and may, at least partially, explain the muscle-specific symptoms of HML.

p53 isoforms regulate astrocyte-mediated neuroprotection and neurodegeneration.

Bidirectional interactions between astrocytes and neurons have physiological roles in the central nervous system and an altered state or dysfunction of such interactions may be associated with neurodegenerative diseases, such as Alzheimer's disease (AD) and amyotrophic lateral sclerosis (ALS). Astrocytes exert structural, metabolic and functional effects on neurons, which can be either neurotoxic or neuroprotective. Their neurotoxic effect is mediated via the senescence-associated secretory phenotype (SASP) involving pro-inflammatory cytokines (e.g., IL-6), while their neuroprotective effect is attributed to neurotrophic growth factors (e.g., NGF). We here demonstrate that the p53 isoforms Δ133p53 and p53ß are expressed in astrocytes and regulate their toxic and protective effects on neurons. Primary human astrocytes undergoing cellular senescence upon serial passaging in vitro showed diminished expression of Δ133p53 and increased p53ß, which were attributed to the autophagic degradation and the SRSF3-mediated alternative RNA splicing, respectively. Early-passage astrocytes with Δ133p53 knockdown or p53ß overexpression were induced to show SASP and to exert neurotoxicity in co-culture with neurons. Restored expression of Δ133p53 in near-senescent, otherwise neurotoxic astrocytes conferred them with neuroprotective activity through repression of SASP and induction of neurotrophic growth factors. Brain tissues from AD and ALS patients possessed increased numbers of senescent astrocytes and, like senescent astrocytes in vitro, showed decreased Δ133p53 and increased p53ß expression, supporting that our in vitro findings recapitulate in vivo pathology of these neurodegenerative diseases. Our finding that Δ133p53 enhances the neuroprotective function of aged and senescent astrocytes suggests that the p53 isoforms and their regulatory mechanisms are potential targets for therapeutic intervention in neurodegenerative diseases.

Serine Arginine-Rich Splicing Factor 1 (SRSF1) Contributes to the Transcriptional Activation of CD3ζ in Human T Cells.

T lymphocytes from many patients with systemic lupus erythematosus (SLE) express decreased levels of the T cell receptor (TCR)-associated CD3 zeta (ζ) signaling chain, a feature directly linked to their abnormal phenotype and function. Reduced mRNA expression partly due to defective alternative splicing, contributes to the reduced expression of CD3ζ chain. We previously identified by oligonucleotide pulldown and mass spectrometry approaches, the serine arginine-rich splicing factor 1 (SRSF1) binding to the 3' untranslated region (UTR) of CD3ζ mRNA. We showed that SRSF1 regulates alternative splicing of the 3'UTR of CD3ζ to promote expression of the normal full length 3`UTR over an unstable splice variant in human T cells. In this study we show that SRSF1 regulates transcriptional activation of CD3ζ. Specifically, overexpression and silencing of SRSF1 respectively increases and decreases CD3ζ total mRNA and protein expression in Jurkat and primary T cells. Using promoter-luciferase assays, we show that SRSF1 enhances transcriptional activity of the CD3ζ promoter in a dose dependent manner. Chromatin immunoprecipitation assays show that SRSF1 is recruited to the CD3ζ promoter. These results indicate that SRSF1 contributes to transcriptional activation of CD3ζ. Thus our study identifies a novel mechanism whereby SRSF1 regulates CD3ζ expression in human T cells and may contribute to the T cell defect in SLE.