Respiratory syncytial virus (RSV) infection causes bronchiolitis and pneumonia in infants.RSV has a linear single-stranded RNA genome encoding 11 proteins, 2 of which are nonstructural (NS1 and NS2). RSV specifically downregulates STAT2 protein expression, thus enabling the virus to evade the host type I interferon response. Degradation of STAT2 requires proteasomal activity and is dependent on the expression of RSV NS1 and NS2 (NS1/2). Here we investigate whether RSV NS proteins can assemble ubiquitin ligase (E3) enzymes to target STAT2 to the proteasome. We demonstrate that NS1 contains elongin C and cullin 2 binding consensus sequences and can interact with elongin C and cullin 2 in vitro; therefore, NS1 has the potential to act as an E3 ligase. By knocking down expression of specific endogenous E3 ligase components using small interfering RNA, NS1/2, or RSV-induced STAT2, degradation is prevented. These results indicate that E3 ligase activity is crucial for the ability of RSV to degrade STAT2. These data may provide the basis for therapeutic intervention against RSV and/or logically designed live attenuated RSV vaccines.Human respiratory syncytial virus (RSV) is the leading cause of severe lower respiratory tract infections in infants and young children (28,31). RSV belongs to the genus Pneumovirus in the subfamily Pneumovirinae of the family Paramyxoviridae. It is an enveloped, nonsegmented negative-strand RNA virus encoding 11 proteins, including nucleocapsid proteins (N, P, and L), surface proteins (F and G), and a matrix protein (M). In addition, the genome encodes two nonstructural proteins (NS1 and NS2), the functions of which are less clearly defined. RSV primarily infects epithelial cells of the respiratory tract and replicates exclusively in the cytoplasm. Progeny RSV particles exit the host cell by budding through the apical surfaces of polarized cells (35).In order to combat such infections, the immune system has evolved a potent antiviral response. Mediators, known as the type I interferons (alpha interferon [IFN-␣] and IFN-␤), stimulate the production of a range of antiviral gene products that limit virus replication and spread (4, 22). The type I IFN receptor consists of two subunits, IFNAR1 and IFNAR2, which are associated with the Janus kinases JAK1 and TYK2, respectively (23). Activation of these receptor tyrosine kinases results in tyrosine phosphorylation of signal transducer and activator of transcription 2 (STAT2) and STAT1. Activated STAT2 and STAT1 associate with interferon regulatory factor 9 (IRF-9) to form the transcriptional activator complex interferon-stimulated gene factor 3 (ISGF-3). These complexes translocate to the nucleus and bind IFN-stimulated response elements (ISRE) to initiate gene transcription and therefore antiviral immunity (8).Wild-type RSV induces a weak type I IFN response following infection (27), suggesting that it has the capacity to evade this host defense mechanism in order to establish a successful infection. RSV is thought to block IFN-␣ and -␤ signaling...

A nanoparticle coated with sialic acid activates Siglec receptors on macrophages, improving survival from sepsis in mice and reducing inflammation in human tissues.

Previous studies have identified the DUB family of cytokine-regulated murine deubiquitinating enzymes, which play a role in the control of cell proliferation and survival. Through data base analyses and cloning, we have identified a human cDNA (DUB-3) that shows significant homology to the known murine DUB family members. Northern blotting has shown expression of this gene in a number of tissues including brain, liver, and muscle, with two transcripts being apparent (1.6 and 1.7 kb). In addition, expression was observed in cell lines including those derived from a number of hematopoietic tumors such as the Burkitt's lymphoma cell line RAJI. We have also demonstrated that DUB-3, which was shown to be an active deubiquitinating enzyme, is induced in response to interleukin-4 and interleukin-6 stimulation. Finally, we have demonstrated that constitutive expression of DUB-3 blocks proliferation and can initiate apoptosis in both IL-3-dependent Ba/F3 cells and NIH3T3 fibroblasts. These findings suggest that human DUB-3, like the murine DUB family members, is transiently induced in response to cytokines and can, when constitutively expressed, block growth factor-dependent proliferation.

Ubiquitination is a reversible posttranslational modification that is essential for cell cycle control, and it is becoming increasingly clear that the removal of ubiquitin from proteins by deubiquitinating enzymes (DUB) is equally important. In this study, we have identified high levels of the DUB USP17 in several tumor-derived cell lines and primary lung, colon, esophagus, and cervix tumor biopsies. We also report that USP17 is tightly regulated during the cell cycle in all the cells examined, being abundantly evident in G 1 and absent in S phase. Moreover, regulated USP17 expression was necessary for cell cycle progression because its depletion significantly impaired G 1 -S transition and blocked cell proliferation. Previously, we have shown that USP17 regulates the intracellular translocation and activation of the GTPase Ras by controlling Ras-converting enzyme 1 (RCE1) activation. RCE1 also regulates the processing of other proteins with a CAAX motif, including Rho family GTPases. We now show that USP17 depletion blocks Ras and RhoA localization and activation. Moreover, our results confirm that USP17-depleted cells have constitutively elevated levels of the cyclin-dependent kinase inhibitors p21 cip1 and p27 kip1 , known downstream targets of Ras and RhoA signaling. These observations clearly show that USP17 is tightly regulated during cell division and that its expression is necessary to coordinate cell cycle progression, and thus, it may be considered a promising novel cancer therapeutic target.

The Ov/Br septin gene, which is also a fusion partner of MLL in acute myeloid leukaemia, is a member of a family of novel GTP binding proteins that have been implicated in cytokinesis and exocytosis. In this study, we describe the genomic and transcriptional organization of this gene, detailing seventeen exons distributed over 240 kb of sequence. Extensive database analyses identi®ed orthologous rodent cDNAs that corresponded to new, unidenti®ed 5' splice variants of the Ov/Br septin gene, increasing the total number of such variants to six. We report that splicing events, occurring at noncanonical sites within the body of the 3' terminal exon, remove either 1801 bp or 1849 bp of non-coding sequence and facilitate access to a secondary open reading frame of 44 amino acids maintained near the end of the 3' UTR. These events constitute a novel coding arrangement and represent the ®rst report of such a design being implemented by a eukaryotic gene. The various Ov/Br proteins either dier minimally at their amino and carboxy termini or are equivalent to truncated versions of larger isoforms. Northern analysis with an Ov/Br septin 3' UTR probe reveals three transcripts of 4.4, 4 and 3 kb, the latter being restricted to a sub-set of the tissues tested. Investigation of the identi®ed Ov/Br septin isoforms by RT ± PCR con®rms a complex transcriptional pattern, with several isoforms showing tissue-speci®c distribution. To date, none of the other human septins have demonstrated such transcriptional complexity. Oncogene (2001) 20, 5930 ± 5939.