Natural killer (NK) cells are lymphocytes involved in antimicrobial and antitumoral immune responses. Using N-ethyl-N-nitrosourea mutagenesis in mice, we identified a mutant with increased resistance to viral infections because of the presence of hyperresponsive NK cells. Whole-genome sequencing and functional analysis revealed a loss-of-function mutation in the Ncr1 gene encoding the activating receptor NKp46. The down-regulation of NK cell activity by NKp46 was associated with the silencing of the Helios transcription factor in NK cells. NKp46 was critical for the subsequent development of antiviral and antibacterial T cell responses, which suggests that the regulation of NK cell function by NKp46 allows for the optimal development of adaptive immune responses. NKp46 blockade enhanced NK cell reactivity in vivo, which could enable the design of immunostimulation strategies in humans.

Upon activation of the ERK and p38 MAPK pathways, the MSK1/2-mediated nucleosomal response, including H3 phosphorylation at serine 28 or 10, is coupled with the induction of immediate-early (IE) gene transcription. The outcome of this response, varying with the stimuli and cellular contexts, ranges from neoplastic transformation to neuronal synaptic plasticity. Here, we used sequential co-immunoprecipitation assays and sequential chromatin immunoprecipitation (ChIP) assays on mouse fibroblast 10T1/2 and MSK1 knockdown 10T1/2 cells to show that H3 serine 28 and 10 phosphorylation leads to promoter remodeling. MSK1, in complexes with phospho-serine adaptor 14-3-3 proteins and BRG1 the ATPase subunit of the SWI/SNF remodeler, is recruited to the promoter of target genes by transcription factors such as Elk-1 or NF-κB. Following MSK1-mediated H3 phosphorylation, BRG1 associates with the promoter of target genes via 14-3-3 proteins, which act as scaffolds. The recruited SWI/SNF remodels nucleosomes at the promoter of IE genes enabling the binding of transcription factors like JUN and the onset of transcription.

Specific, potent, and sustained short hairpin RNA (shRNA)-mediated gene silencing is crucial for the successful application of RNA interference technology to therapeutic interventions. We examined the effects of shRNA expression in primary human lymphocytes (PBLs) using lentiviral vectors bearing different RNA polymerase III promoters. We found that the U6 promoter is more efficient than the H1 promoter for shRNA expression and for reducing expression of CCR5 in PBLs. However, shRNA expression from the U6 promoter resulted in a gradual decline of the transduced cell populations. With one CCR5 shRNA this decline could be attributed to elevated apoptosis but another CCR5 shRNA that caused cytotoxicity did not show evidence of apoptosis, suggesting sequence-specific mechanisms for cytotoxicity. In contrast to the U6 promoter, PBLs transduced by vectors expressing shRNAs from the H1 promoter could be maintained without major cytotoxic effects. Since a lower level of shRNA expression appears to be advantageous to maintaining the shRNA-transduced population, lentiviral vectors bearing the H1 promoter are more suitable for stable transduction and expression of shRNA in primary human T lymphocytes. Our results suggest that functional shRNA screens should include tests for both potency and adverse metabolic effects upon primary cells.

Targeted stable transduction of specific cells is a highly desirable goal for gene therapy applications. We report an efficient and broadly applicable approach for targeting retroviral vectors to specific cells. We find that the envelope of the alphavirus Sindbis virus can pseudotype human immunodeficiency virus type 1-and murine leukemia virus-based retroviral vectors. When modified to contain the Fc-binding domain of protein A, this envelope gives a significant enhancement in specificity in combination with antibodies specific for HLA and CD4 relative to that without antibody. Unlike previous targeting strategies for retroviral transduction, the virus titers are relatively high and stable and can be further increased by ultracentrifugation. This study provides proof of principle for a targeting strategy that would be generally useful for many gene therapy applications.Efficient targeting of specific cells to achieve stable transduction has been attempted by various strategies. Inserting ligands or single-chain antibodies into the retroviral receptor binding envelope subunit has been the most common approach used to alter and/or restrict the host range of retroviral vectors (1,5,7,8,13,14,17,(24)(25)(26). Bridging virus vector and cell by antibodies or ligands is another approach (3,20). In general, most strategies have suffered from inconsistent specificity and low viral titers as a result of modification of the retroviral envelope (1,5,9,13,17,(24)(25)(26). The modified envelope proteins appear to have specific binding activity but have low fusion activity (14, 28), resulting in inefficient entry into cells.The alphavirus Sindbis virus encodes two transmembrane envelope proteins, E1 and E2. E2 is responsible for receptor binding; E1 is responsible for pH-dependent fusion. Unlike retroviruses, the Sindbis virus fusogenic E1 protein can fuse to cells independently of the receptor binding E2 protein (23). Recently, vectors based upon the Sindbis virus RNA genome were constructed whereby the Sindbis virus E2 envelope protein was modified by insertion of an Fc-binding portion (ZZ domain) (12) of protein A (6, 18). These Sindbis virus vectors would bind to and enter cells bearing specific cell surface antigens only in the presence of the appropriate monoclonal antibody (MAb). However, as a lytic RNA virus, Sindbis virus is not suitable for applications requiring stable transduction (6, 21). We tested the possibility that human immunodeficiency virus type 1 (HIV-1)-based vectors could potentially be pseudotyped with Sindbis virus envelope, thereby conferring the targeting properties of the modified Sindbis virus envelope to the HIV-1 vector. MATERIALS AND METHODSPlasmid construction. The expression vector of Sindbis virus envelope protein, plntron SINDBIS, was made by cloning Sindbis virus envelope into pHCMV G (27), replacing the vesicular stomatitis virus G protein. The Sindbis virus envelope fragment was derived from the plasmid TOTO 2000 (kindly provided by Henry Huang). The envelope region of TOTO 2000 was deri...

Statins inhibit 3-hydroxy-3-methyl-glutarylcoenzyme CoA (HMG-CoA) reductase, the proximal enzyme for cholesterol biosynthesis. They exhibit pleiotropic effects and are linked to health benefits for diseases including cancer and lung disease. Understanding their mechanism of action could point to new therapies, thus we investigated the response of primary cultured human airway mesenchymal cells, which play an effector role in asthma and chronic obstructive lung disease (COPD), to simvastatin exposure. Simvastatin induced apoptosis involving caspase-9, -3 and -7, but not caspase-8 in airway smooth muscle cells and fibroblasts. HMG-CoA inhibition did not alter cellular cholesterol content but did abrogate de novo cholesterol synthesis. Pro-apoptotic effects were prevented by exogenous mevalonate, geranylgeranyl pyrophosphate and farnesyl pyrophosphate, downstream products of HMG-CoA. Simvastatin increased expression of Bax, oligomerization of Bax and Bak, and expression of BH3-only p53-dependent genes, PUMA and NOXA. Inhibition of p53 and silencing of p53 unregulated modulator of apoptosis (PUMA) expression partly counteracted simvastatin-induced cell death, suggesting a role for p53-independent mechanisms. Simvastatin did not induce mitochondrial release of cytochrome c, but did promote release of inhibitor of apoptosis (IAP) proteins, Smac and Omi. Simvastatin also inhibited mitochondrial fission with the loss of mitochondrial Drp1, an essential component of mitochondrial fission machinery. Thus, simvastatin activates novel apoptosis pathways in lung mesenchymal cells involving p53, IAP inhibitor release, and disruption of mitochondrial fission.

The regulation of gene expression through alternative pre-mRNA splicing is common in metazoans and is often controlled by intracellular signaling pathways that are important in cell physiology. We have shown that the alternative splicing of a number of genes is controlled by membrane depolarization and Ca 2؉ /calmodulin-dependent protein kinase IV (CaMKIV) through CaMKIV-responsive RNA elements (CaRRE1 and CaRRE2); however, the trans-acting factors remain unknown. Here we show that the heterogeneous nuclear ribonucleoprotein (hnRNP) L is a CaRRE1 binding factor in nuclear extracts. An hnRNP L high affinity CA (cytidine-adenosine) repeat element is sufficient to mediate CaMKIV and hnRNP L repression of splicing in a location (3-splice site proximity)-dependent way. Depletion of hnRNP L by RNA interference followed by rescue with coexpressed exogenous hnRNP L demonstrates that hnRNP L mediates the CaMKIV-regulated splicing through CA repeats in heterologous contexts. Depletion of hnRNP L also led to increased inclusion of the stress axis-regulated exon and a CA repeat-harboring exon under depolarization or with activated CaMKIV. Moreover, hnRNP L binding to CaRRE1 was increased by CaMKIV and, conversely, was reduced by pretreatments with protein phosphatases. Therefore, hnRNP L is an essential component of CaMKIV-regulated alternative splicing through CA repeats, with its phosphorylation likely playing a critical role.Alternative pre-mRNA splicing allows the generation of multiple protein isoforms from a single transcript, contributing greatly to proteomic complexity (1-6). It is essential for normal cell function, and aberrant splicing is implicated in the development of human genetic diseases (7,8). Many alternative splicing events can be regulated by cell signals and may play important roles in cell physiology (9 -11). However, little is known of the essential molecular components between cell signals and the splicing machinery.Alternative splicing in mammalian systems is often controlled by multiple cis-acting regulatory elements in introns and exons (1, 12). These elements are mostly bound by transacting protein factors and in some cases by small nucleolar RNA (13) or form RNA secondary structures (14). The transacting factors are thought to control the assembly of constitutive splicing components to the target splice sites. For cell signal control of alternative splicing, RNA elements and trans-acting factors have been identified in several systems (9,10,(15)(16)(17)(18)(19)(20)(21)(22)(23).CA repeats are the most abundant and highly polymorphic dinucleotide repeats in the human genome. They are widely used in genetic linkage analyses (24), and their instability is characteristic of the mutator phenotype of cells defective in DNA repair genes (25). Recent studies indicate that long (Ն19 repeats) or short clustered CA repeats in downstream introns are constitutive enhancers or repressors depending on their proximity to the 5Ј-splice site (26,27). These effects are mediated by the heterogeneous nuclear ribonuc...

IL-17A has been shown to be expressed at higher levels in respiratory secretions from asthmatics and to correlate with airway hyperresponsiveness. Although these studies raise the possibility that IL-17A may influence allergic disease, the mechanism remains unknown. We previously demonstrated that IL-17A mediates CC chemokine (CCL11) production from human airway smooth muscle (ASM) cells. In this study, we demonstrate that STAT3 activation is critical in IL-17A-mediated CCL11 expression in ASM cells. IL-17A mediated a rapid phosphorylation of STAT3 but not STAT6 or STAT5 in ASM cells. Interestingly, transient transfection with wild-type or mutated CCL11 promoter constructs showed that IL-17A-mediated CCL11 expression relies on the STAT6 binding site. However, STAT3 but not STAT6 in vivo binding to the CCL11 promoter was detected following IL-17A stimulation of ASM cells. Overexpression of DN STAT3 (STAT3β) abolishes IL-17A-induced CCL11 promoter activity. This effect was not observed with STAT6 DN or the STAT3 mutant at Ser727. Interestingly, disruption of STAT3 activity with the SH2 domain binding peptide, but not with control peptide, results in a significant reduction of IL-17A-mediated STAT3 phosphorylation and CCL11 promoter activity. IL-17A-mediated CCL11 promoter activity and mRNA were significantly diminished in STAT3- but not STAT6-silenced ASM cells. Finally, IL-17A-induced STAT3 phosphorylation was sensitive to pharmacological inhibitors of JAK2 and ERK1/2. Taken together, our data provide the first evidence of IL-17A-mediated gene expression via STAT3 in ASM cells. Collectively, our results raise the possibility that the IL-17A/STAT3 signaling pathway may play a crucial role in airway inflammatory responses.

Background: Excitable cells show activity-dependent alternative splicing of ion channels. Results: CaMKIV phosphorylates hnRNP L at Ser-513, which is essential for depolarization-repression of a Slo1 potassium channel exon and splicing factor U2AF65. Conclusion: Depolarization controls alternative splicing of Slo1 channels through Ser-513 phosphorylation and inhibition of U2AF65.Significance: This provides the first direct link between depolarization/CaMKIV and the constitutive spliceosome.