Analogies between Drosophila and mammalian TRAF pathways

Laboratory-simulated marine heatwave enhances physiological damage to mussels exposed to titanium dioxide nanoparticles by disrupting the gut-hepatopancreas axis

The aggregation state of nano-TiO2 in the environment is altered under marine heatwaves (MHWs), thus affecting its bioavailability and toxicity to the marine organisms. Here, we investigated the toxic mechanisms and effects of nano-TiO2 on gut-hepatopancreas axis health of Mytilus coruscus exposed to 25 and 250 μg/L of nano-TiO2 under laboratory-simulated MHW. Compared with the control conditions or post-MHW cooling phase, prolonged MHW exposure significantly inhibited digestive function, decreased immune-related enzymes activities, and caused neurotoxicity in the mussels. 16S rRNA analysis demonstrated that high concentration nano-TiO2 and combined exposures decreased the abundance of Bacteroidota while increased the Proteobacteria. Additionally, the elevated pro-inflammatory bacteria released endotoxin lipopolysaccharide (LPS), which activated Toll-like receptor 4 (TLR-4) in the hepatopancreas and induced hepatopancreatic inflammation by downregulating nuclear factor-kappa B (NF-κB) signaling pathway and detoxification-related genes. Furthermore, nano-TiO2 and MHW exposure dysregulated the glutathione system, decreased the levels of antioxidation-related genes, and induced the accumulation of ROS and lipid peroxide (LPO) contents, thus causing severe oxidative damage and hepatopancreatic cell apoptosis. These findings demonstrate that nano-TiO2 and MHW induce hepatopancreatic inflammation and cell damage, which are strongly associated with the gut lesions and disrupted gut-hepatopancreas axis homeostasis.

The involvement of tumor necrosis factor receptor-associated factor 6 in regulating immune response by NF-κB at pre-molt stage of Chinese mitten crab (Eriocheir sinensis)

Molting is a crucial biological process of crustaceans. Crustaceans go through three separate stages throughout their molting process, including pre-molt, post-molt and inter-molt. However, the exact mechanism of immunological modulation during molting remains unclear. Tumor necrosis factor receptor-associated factor 6 (TRAF6) has been extensively documented to participate in immune defense. In the present study, a TRAF6 gene with two TRAF-type zinc finger domains was identified from Eriocheir sinensis (designed as EsTRAF6), and its role in regulating immune response during molting process was explored. The mRNA expression level of EsTRAF6 at pre-molt stage was higher than that at post-molt stage and inter-molt stage. After Aeromonas hydrophila stimulation, the expression levels of EsTRAF6, EsRelish and anti-lipopolysaccharide factors (ALFs) genes exhibited a considerable increase at three molting stages. Subsequently, the expression patterns of EsTRAF6 and EsRelish in response to the treatment with 20-hydroxyecdysone (20E) were examined. The mRNA expression of EsTRAF6 and EsRelish were significantly increased at 12 h after 20E injection. Additionally, the protein expression level of TRAF6 was also up-regulated in 20E group compared to control group. Furthermore, the role of EsTRAF6 in regulating the anti- ALFs expression at pre-molt stage post A. hydrophila stimulation was investigated. Following the inhibition of the EsTRAF6 transcript using RNAi or the injection of inhibitor (TMBPS), there was a notable decrease of the EsALF1, EsALF2 and EsALF3 transcripts. Moreover, a significant reduction in the phosphorylation level of NF-κB at pre-molt stage was observed after A. hydrophila stimulation in TRAF6-inhibited crabs. Collectively, our results suggest that EsTRAF6 could be induced by 20E and promoted the EsALFs expression by activating NF-κB at pre-molt stage, which provides a novel insight into the research of immune regulatory mechanism during the process of molting of crustaceans.

OTU7B Modulates the Mosquito Immune Response to Beauveria bassiana Infection via Deubiquitination of the Toll Adaptor TRAF4

The Aedes aegypti mosquito transmits devastating flaviviruses, such as Zika, dengue, and yellow fever viruses. For more effective control of the vector, the pathogenicity of Beauveria bassiana, a fungus commonly used for biological control of pest insects, may be enhanced based on in-depth knowledge of molecular interactions between the pathogen and its host. Here, we identified a mechanism employed by B. bassiana, which efficiently blocks the Ae. aegypti antifungal immune response by a protease that contains an ovarian tumor (OTU) domain. RNA-sequencing analysis showed that the depletion of OTU7B significantly upregulates the mRNA level of immunity-related genes after a challenge of the fungus. CRISPR-Cas9 knockout of OTU7B conferred a higher resistance of mosquitoes to the fungus B. bassiana. OTU7B suppressed activation of the immune response by preventing nuclear translocation of the NF-κB transcription factor Rel1, a mosquito orthologue of Drosophila Dorsal. Further studies identified tumor necrosis factor receptor-associated factor 4 (TRAF4) as an interacting protein of OTU7B. TRAF4-deficient mosquitoes were more sensitive to fungal infection, indicating TRAF4 to be the adaptor protein that activates the Toll pathway. TRAF4 is K63-link polyubiquitinated at K338 residue upon immune challenge. However, OTU7B inhibited the immune signaling by enzymatically removing the polyubiquitin chains of mosquito TRAF4. Thus, this study has uncovered a novel mechanism of fungal action against the host innate immunity, providing a platform for further improvement of fungal pathogen effectiveness. IMPORTANCE Insects use innate immunity to defend against microbial infection. The Toll pathway is a major immune signaling pathway that is associated with the antifungal immune response in mosquitoes. Our study identified a fungal-induced deubiquitinase, OTU7B, which, when knocked out, promotes the translocation of the NF-κB factor Rel1 into the nucleus and confers enhanced resistance to fungal infection. We further found the counterpart of OTU7B, TRAF4, which is a component of the Toll pathway and acts as an adaptor protein. OTU7B enzymatically removes K63-linked polyubiquitin chains from TRAF4. The immune response is suppressed, and mosquitoes become much more sensitive to the Beauveria bassiana infection. Our findings reveal a novel mechanism of fungal action against the host innate immunity.

TNF-Receptor-Associated Factor 3 in Litopenaeus vannamei Restricts White Spot Syndrome Virus Infection Through the IRF-Vago Antiviral Pathway

Tumor necrosis factor receptor (TNFR)-associated factors (TRAFs) are vital signaling adaptor proteins for the innate immune response and are involved in many important pathways, such as the NF-κB- and interferon regulatory factor (IRF)-activated signaling pathways. In this study, the TRAF3 ortholog from the shrimp Litopenaeus vannamei (LvTRAF3) was cloned and characterized. LvTRAF3 has a transcript of 3,865 bp, with an open reading frame (ORF) of 1,002 bp and encodes a polypeptide of 333 amino acids, including a conserved TRAF-C domain. The expression of LvTRAF3 in the intestine and hemocyte was up-regulated in response to poly (I:C) challenge and white spot syndrome virus (WSSV) infection. RNAi knockdown of LvTRAF3 in vivo significantly increased WSSV gene transcription, viral loads, and mortality in WSSV-infected shrimp. Next, we found that LvTRAF3 was not able to induce the activation of the NF-κB pathway, which was crucial for synthesis of antimicrobial peptides (AMPs), which mediate antiviral immunity. Specifically, in dual-luciferase reporter assays, LvTRAF3 could not activate several types of promoters with NF-κB binding sites, including those from WSSV genes (wsv069, wsv056, and wsv403), Drosophila AMPs or shrimp AMPs. Accordingly, the mRNA levels of shrimp AMPs did not significantly change when TRAF3 was knocked down during WSSV infection. Instead, we found that LvTRAF3 signaled through the IRF-Vago antiviral cascade. LvTRAF3 functioned upstream of LvIRF to regulate the expression of LvVago4 and LvVago5 during WSSV infection in vivo. Taken together, these data provide experimental evidence of the participation of LvTRAF3 in the host defense to WSSV through the activation of the IRF-Vago pathway but not the NF-κB pathway.

Genome-wide characterization of TNF receptor-associated factors in the Chinese soft-shelled turtle Pelodiscus sinensis and their expression profiling in response to Aeromonas hydrophila challenge

Tumor necrosis factor receptor (TNFR)-associated factors (TRAFs) are a family of crucial signaling molecules that mediate the signal transduction of various immune signaling pathways. Extensive studies have demonstrated that TRAFs play vital roles in regulating cellular immune responses. However, the biological functions and expression profiling of TRAFs in Chinese soft-shelled turtle (Pelodiscus sinensis) remain unclear. In this study, the genes of the PsTRAF family at the genome-wide level were identified in P. sinensis, revealing six PsTRAF members that contained the conserved TRAF domain in the C-terminal regions. Molecular evolutionary analysis showed that PsTRAFs shared close evolutionary relationships and similar protein crystal structures with the TRAF homologs from other turtles, indicating the evolutionary conservation of PsTRAFs. Further expression analysis revealed the tissue-specific expression of PsTRAF genes. Obvious variations in the expression of PsTRAF genes were observed in the spleen in response to Aeromonas hydrophila infection. Three PsTRAF genes, PsTRAF2, PsTRAF3, and PsTRAF6, were significantly upregulated at the mRNA and protein levels post-infection, indicating their potential function in the immune response. Moreover, the protein-protein associations of PsTRAFs with several signaling receptors were predicted in P. sinensis. These results provide a basis for the investigation of the functional roles of PsTRAFs in immune defense against bacterial infection.

Two novel serine proteases from Scylla paramamosain involved in the synthesis of anti-lipopolysaccharide factors and activation of prophenoloxidase system

Serine proteases (SPs) are important in various immune responses, including prophenoloxidase (proPO) activation, antimicrobial peptides (AMPs) synthesis, and hemolymph coagulation in invertebrates. In this study, SP3 and SP5 of mud crab (Scylla paramamosain) were studied. SP3 and SP5 were expressed in all examined tissues (mainly in hemocytes), and are associated with the immune responses of mud crab to Vibrio parahemolyticus and Staphylococcus aureus, as well as interacted with TRAF6, and are involved in the activation of anti-lipopolysaccharide factors (ALFs) probably through the TLR/NF-κB pathway. Depletion of SP3 inhibited the expression of ALF1, ALF2, ALF3, and ALF6, while knockdown of SP5 significantly decreased ALF5, and ALF6. Furthermore, both SP5 and TRAF6 regulated the PO activity in the hemolymph of mud crab. Overexpression assay showed that both SP3 and SP5 could enhance the promoter activities of ALFs in mud crab. Taken together, the results of this study indicate that SP3 and SP5 might play important roles in the immune system of mud crab against pathogen invasion.

Molecular cloning and functional analysis of tumor necrosis factor receptor-associated factor 6 (TRAF6) in thick shell mussel, Mytilus coruscus

Tumor necrosis factor receptor-associated factor 6 (TRAF6) is one of the key adapter molecules in Toll-like receptor signal transduction that triggers downstream cascades involved in innate immunity. Despite of the well study in vertebrates, there is few data ascribe to this TRAF member in invertebrates, especially in bivalves. In the present study, a novel TRAF6 homologue termed McTRAF6 was firstly characterized in Mytilus coruscus. Like its counterparts in mammals, McTRAF6 shared the domain topology containing one RING domain, two zinc finger domains, one coiled-coil region and a MATH domain. McTRAF6 transcripts predominantly expressed in gills, digestive glands and hemocytes in M. coruscus, and were significantly up-regulated in hemocytes after challenge with lipopolysaccharide (LPS) and polyinosine-polycytidylic acid (poly I:C). Further, the subcellular localization in cytoplasm and the activation of Nk-κB or ISRE luciferase reporter by overexpressed McTRAF6 were identified in HEK293T cells. These results collectively indicate that McTRAF6 is a member of TRAF6 subfamily and plays a potential role in immune defense system against pathogenic agents invasions in thick shell mussel. To our knowledge, this is the first report on component of TLR signaling pathway in thick shell mussel, providing further evidence for the existence of TLR pathway in M. coruscus and contribute to clarify the innate immune system of thick shell mussel.

Tumor necrosis factor receptor-associated factor 6 (TRAF6) participates in peroxinectin gene expression in Fenneropenaeus penicillatus

Tumor necrosis factor receptor-associated factor 6 (TRAF6) is an important cytoplasm signal adaptor that mediates signals activated by tumor necrosis factor receptor (TNFR) superfamily and the Interleukin-1 receptor/Toll-like receptor (IL-1/TLR) superfamily. In the study, the full-length cDNA of a TRAF6 homolog (FpTRAF6) was identified from Fenneropenaeus penicillatus. The full-length cDNA of FpTRAF6 is 2033 bp long, with an open reading frame (ORF) encoding a putative protein of 594 amino acids, including a RING type Zinc finger, two TRAF-type Zinc fingers, and a conserved C-terminal meprin and TRAF homology (MATH) domain. The overall amino acid sequence identity between FpTRAF6 and other TRAF6s ranged from 62.7 to 94.1% for crustaceans and from 45.6 to 59.3% for mollusca. Real-time qRT-PCR indicated that FpTRAF6 was constitutively expressed in various tissues of F. penicillatus. The temporal expression patterns of FpTRAF6 mRNA were different in the different tissues after microbial challenge. FpTRAF6 was downregulated in the heart, no obvious changes in the gill, intestine and hemocytes, and upregulated in other tested tissues after WSSV challenge. After V. alginolyticus injection, FpTRAF6 was downregulated in the heart and intestine, upregulated in the gill, lymphoid organ and hematopoietic organ, and no obvious changes in other tested tissues. RNAi assay was carried out to investigate the function of FpTRAF6. The results showed that silencing FpTRAF6 gene could inhibit peroxinectin expression in vivo, and enhance the sensitivity of shrimps to WSSV and V. alginolyticus challenge, suggesting FpTRAF6 could play a positive role against bacterial and viral pathogens. In conclusion, the results of the study provide some insights into the function of FpTRAF6 in activating TLRs signaling pathway and the host defense against invading pathogens.

Tumor necrosis factor receptor-associated factor 6 (TRAF6) participates in anti-lipopolysaccharide factors (ALFs) gene expression in mud crab

Tumor necrosis factor receptor-associated factor 6 (TRAF6) is a key cytoplasm signal adaptor that mediates signals activated by tumor necrosis factor receptor (TNFR) superfamily and the Interleukin-1 receptor/Toll-like receptor (IL-1/TLR) superfamily. The full-length 2492 bp TRAF6 (Sp-TRAF6) from Scylla paramamosain contains 1800 bp of open reading frame (ORF) encoding 598 amino acids, including an N-terminal RING-type zinc finger, two TRAF-type zinc fingers and a conserved C-terminal meprin and TRAF homology (MATH) domain. Multiple alignment analysis shows that the putative amino acid sequence of Sp-TRAf6 has highest identity of 88% with Pt-TRAF6 from Portunus trituberculatus, while the similarity of Sp-TRAF6 with other crustacean sequences was 54-55%. RT-PCR analysis indicated that Sp-TRAF6 transcripts were predominantly expressed in the hepatopancreas and stomach, whereas it was barely detected in the heart and hemocytes in our study. Moreover, Sp-TRAF6 transcripts were significantly up-regulated after Vibrio parahemolyticus and LPS challenges. RNA interference assay was carried out used by siRNA to investigate the genes expression patterns regulated by Sp-TRAF6. The qRT-PCR results showed that silencing Sp-TRAF6 gene could inhibit SpALF1, SpALF2, SpALF5 and SpALF6 expression in hemocytes, while inhibit SpALF1, SpALF3, SpALF4, SpALF5 and SpALF6 expression in hepatopancreas. Taken together, the acute-phase response to immune challenges and the inhibition of SpALFs gene expression indicate that Sp-TRAF6 plays an important role in host defense against pathogen invasions via regulation of ALF gene expression in S. paramamosain.

First description and expression analysis of tumor necrosis factor receptor-associated factor 6 (TRAF6) from the swimming crab, Portunus trituberculatus

Tumor necrosis factor receptor-associated factor 6 (TRAF6) is a cytoplasmic adapter protein that mediates signals induced by the tumor necrosis factor receptor (TNFR) superfamily and the interleukin-1 receptor (IL-1R). In the present study, the full-length cDNA of TRAF6 (Pt-TRAF6) was identified in a marine crab, Portunus trituberculatus. Pt-TRAF6 ORF is predicted to encode a 599-amino acid protein, including a RING type zinc finger, two TRAF-type zinc fingers, and a meprin and TRAF homology (MATH) domain. The overall amino acid sequence identity between Pt-TRAF6 and other TRAF6s ranged from 50.9 to 51.3% for shrimp and from 16.1 to 19.4% for insects. The Pt-TRAF6 gene contains six exons and five introns, which is different from the organization of the insect TRAF6 gene. Pt-TRAF6 transcripts were broadly expressed in all tissues tested, and their expression was higher in hemocytes, gills, the intestine, and heart than in muscle. Interestingly, the level of Pt-TRAF6 transcript differed between male and female crabs. After Vibrio alginolyticus or lipopolysaccharide (LPS) challenge, the Pt-TRAF6 transcript was down-regulated in hemocytes and up-regulated in gills. Moreover, Pt-TRAF6 expression was altered sooner in the LPS challenge group than in the V. alginolyticus challenge group. These results indicate that Pt-TRAF6 may respond to Gram-negative bacterial infections.

A comprehensive analysis of the Manduca sexta immunotranscriptome

As a biochemical model, Manduca sexta has substantially contributed to our knowledge on insect innate immunity. The RNA-Seq approach was implemented in three studies to examine tissue immunotranscriptomes of this species. With the latest and largest focusing on highly regulated process- and tissue-specific genes, we further analyzed the same set of data using BLAST2GO to explore functional aspects of the larval fat body (F) and hemocyte (H) transcriptomes with (I) or without (C) immune challenge. Using immunity-related sequences from other insects, we found 383 homologous contigs and compared them with those discovered based on relative abundance changes. The major overlap of the two lists validated our previous research designed for gene discovery and transcript profiling in organisms lacking sequenced genomes. By concatenating the contigs, we established a repertoire of 232 immunity-related genes encoding proteins for pathogen recognition (16%), signal transduction (53%), microbe killing (13%) and others (18%). We examined their transcript levels along with attribute classifications and detected prominent differences in nine of the 30 level 2 gene ontology (GO) categories. The increase in extracellular proteins (155%) was consistent with the highly induced synthesis of defense molecules (e.g., antimicrobial peptides) in fat body after the immune challenge. We identified most members of the putative Toll, IMD, MAPK-JNK-p38 and JAK-STAT pathways and small changes in their mRNA levels. Together, these findings set the stage for on-going analysis of the M. sexta immunogenome.

Atlas of signaling for interpretation of microarray experiments

Microarray-based expression profiling of living systems is a quick and inexpensive method to obtain insights into the nature of various diseases and phenotypes. A typical microarray profile can yield hundreds or even thousands of differentially expressed genes and finding biologically plausible themes or regulatory mechanisms underlying these changes is a non-trivial and daunting task. We describe a novel approach for systems-level interpretation of microarray expression data using a manually constructed “overview” pathway depicting the main cellular signaling channels (Atlas of Signaling). Currently, the developed pathway focuses on signal transduction from surface receptors to transcription factors and further transcriptional regulation of cellular “workhorse” proteins. We show how the constructed Atlas of Signaling in combination with an enrichment analysis algorithm allows quick identification and visualization of the main signaling cascades and cellular processes affected in a gene expression profiling experiment. We validate our approach using several publicly available gene expression datasets.

TRAF6 ubiquitin ligase is essential for RANKL signaling and osteoclast differentiation

Tumor necrosis factor receptor-associated factor 6 (TRAF6), the crucial adaptor molecule of receptor activator of NF-kappaB (RANK), plays an essential role in governing the formation of multi-nucleated osteoclasts. TRAF6 is a RING-dependent ubiquitin (Ub) ligase that in conjunction with Ubc13/Uev1A catalyzes its own auto-ubiquitination via Lys63-linked poly-Ub chains. While the receptor-adaptor function of TRAF6 in RANK signaling is well understood, the significance of its Ub ligase activity in this process remains largely unknown. In this study, we show that retroviral expression of TRAF6, but not a RING mutant of TRAF6 was able to rescue TRAF6-deficient monocytes for the activation of IKK and osteoclast differentiation by RANKL. Furthermore, a catalytically inactive Ubc13 or stable knockdown of Ubc13 significantly prevents RANK-mediated TRAF6 ubiquitination and NF-kappaB and JNK activation. These data establish a signaling cascade in which regulated Lys63-linked TRAF6 auto-ubiquitination is the critical upstream mediator of osteoclast differentiation.

Inhibition of RANKL-mediated osteoclast differentiation by selective TRAF6 decoy peptides

RANK and RANKL are essential mediators of osteoclastogenesis. RANK interacts with members of the tumor necrosis factor receptor-associated factor (TRAF) family, of which TRAF6 is the critical signaling molecule. We identified a unique TRAF6-binding motif in RANK, which was subsequently co-crystallized with TRAF6 revealing distinct molecular interactions. A cell-permeable TRAF6 decoy peptide (T6DP) was shown to specifically target TRAF6 and inhibit RANKL-mediated signaling. In this study, we identified a core motif for binding to TRAF6 by generating a series of deletion mutants linked via palmitate as a means to internalize the peptide, thus making a smaller scaffold for intracellular delivery. The core motif of RKIPTEDEY inhibited RANKL-mediated osteoclastogenesis and bone resorption. In contrast, TRAF2/5 decoy peptides appeared to have no affect. Thus, disruption of the RANK-TRAF6 interaction may prove useful as a novel target for the development of a small molecule therapeutic agent for the treatment of bone-related diseases.

Novel activity of an anti-inflammatory cytokine: IL-10 prevents TNFalpha-induced resistance to IGF-I in myoblasts

IL-10 is an anti-inflammatory cytokine that suppresses synthesis of proinflammatory cytokines and their receptors. Here we tested the possibility that TNFalpha-induced hormone resistance in myoblasts might be overcome by IL-10. We found that IL-10 restores myogenesis by suppressing the ability of exogenous TNFalpha to inhibit IGF-I-induced myogenin. This protection occurs without decreasing global activity of TNF receptors since IL-10 does not impair TNFalpha-induced IL-6 synthesis or ERK1/2 phosphorylation. Instead, IL-10 acts to prevent TNFalpha-induced phosphorylation of JNK. These findings demonstrate that IL-10 serves a previously unrecognized protective role in muscle progenitors by overcoming TNFalpha-induced resistance to IGF-I.

Genetic deletion of JNK1 and JNK2 aggravates the DSS-induced colitis in mice

The c-Jun N-terminal kinases (JNKs) are considered as novel targets for therapy of inflammatory bowel diseases (IBD). However, the relevant JNK isoforms have to be elucidated. Here, we analyze the individual contribution of the JNK1 and JNK2 isoforms in a dextran sulfate sodium (DSS) model of experimental colitis. JNK1 and JNK2 knockout mice (JNK1 ko, JNK2 ko) and their wild-type controls (WT1, WT2) received three cycles of DSS treatment, each consisting of 1.7% DSS for 5 days, followed by 5 days with water. Animals were daily evaluated by a disease activity index (DAI) comprising measurement of body weight, estimation of stool consistency, and test for occult blood/gross rectal bleeding. After 30 days all animals were sacrificed, and the inflamed intestine was histologically evaluated by a crypt damage score. Unexpectedly, neither JNK1 ko nor JNK2 ko prevented mice from developing a chronic colitis when compared to wild-type controls WT1 and WT2, respectively. On the contrary, DAI and mortality were aggravated in JNK2 ko compared to WT2. DAI and mortality did not differ between JNK1 ko and WT1, but the histological crypt damage score was significantly enhanced in the cecum of JNK1 ko mice. Genetic deletion of JNK2 worsens the disease outcome in an experimental model of murine colitis. We hypothesize that the functional deletion of the otherwise proapoptotic JNK2 prolongs the activity of proinflammatory immune cells with deterioration of disease activity.

Relationship between nuclear factor-kappa B and cell apoptosis

The roles of nuclear factor-kappa B (NF-κB) fa-mily and its signaling transduction pathway in apoptosis has been the focus of intense investigation all over the world. Researches show that NF-κB signaling pathway exerts anti-apoptotic function via many other proteins, including IAPs, Bcl-2, TRAF, JNK, FLIP, A20, Gadd45b, MnSOD and so on, but the exact mechanism remains unclear. Inhibition of NF-κB activation can promote the process of programmed cell death, and may become new avenues for therapeutic intervention in immune diseases, chronic inflammatory diseases and certain cancers. Furthermore, recent studies reveal that NF-κB can promote apoptosis, and the types and quantity of NF-κB subunits play a key role in apoptosis. In this review, we presented an overview of the progress in the relationship between NF-κB and apoptosis.

Dissecting role of regulatory factors in NF-kappaB pathway with siRNA

NF-kappaB, a family of related transcription factors, has been a focus of intense scientific research during the past decade. Multiple stimuli, both extracellular and intracellular, lead to its activation. The NF-kappaB pathway regulates expression of a diverse array of genes involved in different biological processes. Various pathological states are characterized by the dysregulated NF-kappaB pathway. Recently, NF-kappaB activation has been connected with multiple aspects of oncogenesis and serves as an important mechanism to regulate cell survival in response to chemotherapy by activating different genes that inhibit apoptosis. Several methods of inhibiting NF-kappaB activation, such as antisense oligonucleotides, proteosome inhibitors and RNA interference (RNAi) are currently under investigation. RNAi represents a powerful tool to better define the role of specific genes in different signal transduction pathways and has recently been used to define the function of genes that regulate the NF-kappaB pathway. This review discusses the emerging role of RNAi to dissect the function of regulatory factors in the NF-kappaB pathway and its potential use as a targeted therapy.

Using RNAi to catch Drosophila genes in a web of interactions: insights into cancer research

The completion of whole-genome sequencing of various model organisms and the recent explosion of new technologies in the field of Functional Genomics and Proteomics is poised to revolutionize the way scientists identify and characterize gene function. One of the most significant advances in recent years has been the application of RNA interference (RNAi) as a means of assaying gene function. In the post-genomic era, advances in the field of cancer biology will rely upon the rapid identification and characterization of genes that regulate cell growth, proliferation, and apoptosis. Significant efforts are being directed towards cancer therapy and devising efficient means of selectively delivering drugs to cancerous cells. In this review, we discuss the promise of integrating genome-wide RNAi screens with proteomic approaches and small-molecule chemical genetic screens, towards improving our ability to understand and treat cancer.