No abstract

Retinoic acid-inducible gene-I (RIG-I)-like receptors (RLR) are members of the DEAD box helicases, and recognize viral RNA in the cytoplasm, leading to IFN-b induction through the adaptor IFN-b promoter stimulator-1 (IPS-1) (also known as Cardif, mitochondrial antiviral signaling protein or virus-induced signaling adaptor). Since uninfected cells usually harbor a trace of RIG-I, other RNA-binding proteins may participate in assembling viral RNA into the IPS-1 pathway during the initial response to infection. We searched for proteins coupling with human IPS-1 by yeast two-hybrid and identified another DEAD (Asp-Glu-AlaAsp) box helicase, DDX3 (DEAD/H BOX 3). DDX3 can bind viral RNA to join it in the IPS-1 complex. Unlike RIG-I, DDX3 was constitutively expressed in cells, and some fraction of DDX3 is colocalized with IPS-1 around mitochondria. The 622-662 a.a DDX3 C-terminal region (DDX3-C) directly bound to the IPS-1 CARD-like domain, and the whole DDX3 protein also associated with RLR. By reporter assay, DDX3 helped IPS-1 up-regulate IFN-b promoter activation and knockdown of DDX3 by siRNA resulted in reduced IFN-b induction. This activity was conserved on the DDX3-C fragment. DDX3 only marginally enhanced IFN-b promoter activation induced by transfected TANK-binding kinase 1 (TBK1) or I-kappa-B kinase-e (IKKe). Forced expression of DDX3 augmented virus-mediated IFN-b induction and host cell protection against virus infection. Hence, DDX3 is an antiviral IPS-1 enhancer. IntroductionRetinoic acid-inducible gene-I (RIG-I) and melanoma differentiation-associated gene 5 (MDA5) are cytoplasmic RNA helicases [1][2][3], which signal the presence of viral RNA through the adaptor, IFN-b promoter stimulator-1 (IPS-1) (also known as mitochondrial antiviral signaling protein/caspase recruitment domain (CARD) adaptor inducing IFN-b (Cardif)/virus-induced signaling adaptor) to produce . IPS-1 localizes on the outer membrane of the mitochondria via its C-terminus [6]. Its Nterminus consists of a CARD domain, which interacts with the CARD domains of RIG-I and MDA5. Viral RNA resulting from penetration or replication are believed to assemble in the CARDinteracting helicase complex to activate the cytoplasmic IFNinducing pathway. Although non-infected cells usually express minimal amounts of RIG-I/MDA5, the final output of type I IFN is efficiently induced at an early stage of infection to protect host cells from viral spreading.Once IPS-1 is activated, the kinase complex consisting of TANK-homologous proteins and virus-activated kinases induce nuclear translocation of IFN regulatory factor-3 (IRF-3) to activate the IFN promoter [8]. NAK-associated protein 1, TANKbinding kinase 1 (TBK1) and I-kappa-B kinase-e (IKKe) are components of the kinase complex that phosphorylates IRF-3 to induce type I IFN [9,10]. RIG-I recognizes products of various RNA viruses, while MDA5 recognizes products of picornaviruses 940Frontline [1,11]. RIG-I and MDA5 share the helicase domain, which is classified into the DEAD (Asp-Glu-Ala-Asp) box helicase...

Systemic and localized scleroderma (SSc and LSc) is characterized by excessive deposition of collagen and tissue fibrosis in the skin. Although they have fundamental common characteristics including autoimmunity, little is known about the exact mechanism that mediates the excessive collagen expression in these disorders. In the current study, we tried to evaluate the possibility that microRNAs (miRNAs) play some roles in the pathogenesis of fibrosis seen in these diseases. miRNA expression patterns were evaluated by miRNA array analysis, real-time PCR, and in situ hybridization. The function of miRNAs in dermal fibroblasts was assessed using miRNA inhibitors, precursors, or protectors. In the mouse model of bleomycin-induced dermal sclerosis, the overexpression of miRNAs was performed by i.p. miRNA injection. We demonstrated let-7a expression was downregulated in SSc and LSc skin both in vivo and in vitro, compared with normal or keloid skin. The inhibition or overexpression of let-7a in human or mouse skin fibroblasts affected the protein expression of type I collagen or luciferase activity of collagen 3′-untranslated region. Also, we found let-7a was detectable and quantitative in the serum and investigated serum let-7a levels in patients with SSc or LSc. let-7a concentration was significantly decreased in these patients, especially in LSc patients. Moreover, we revealed that the intermittent overexpression of let-7a in the skin by i.p. miRNA injection improved the skin fibrosis induced by bleomycin in mice. Investigation of more detailed mechanisms of miRNA-mediated regulation of collagen expression may lead to new therapeutic approaches against SSc and LSc.

Cell morphogenesis is of fundamental significance in all eukaryotes for development, differentiation, and cell proliferation. In fission yeast, Drosophila Furry-like Mor2 plays an essential role in cell morphogenesis in concert with the NDR/Tricornered kinase Orb6. Mutations of these genes result in the loss of cell polarity. Here we show that the conserved proteins, MO25-like Pmo25, GC kinase Nak1, Mor2, and Orb6, constitute a morphogenesis network that is important for polarity control and cell separation. Intriguingly, Pmo25 was localized at the mitotic spindle pole bodies (SPBs) and then underwent translocation to the dividing medial region upon cytokinesis. Pmo25 formed a complex with Nak1 and was required for both the localization and kinase activity of Nak1. Pmo25 and Nak1 in turn were essential for Orb6 kinase activity. Further, the Pmo25 localization at the SPBs and the Nak1-Orb6 kinase activities during interphase were under the control of the Cdc7 and Sid1 kinases in the septation initiation network (SIN), suggesting a functional linkage between SIN and the network for cell morphogenesis/separation following cytokinesis.

Decreased miR-424 expression and subsequently increased MEK1 or cyclin E1 may play a key role in the pathogenesis of psoriasis. Investigation of the regulatory mechanisms of keratinocyte proliferation by miRNA may lead to new treatments and a disease activity marker.