Japan. 8 These authors contributed equally to this work. Correspondence should be addressed to A.T. (takaoka@igm.hokudai.ac.jp). At least three DExD/H-box RNA helicases 4,5 , RIG-I, MDA5 and LGP2 are included in the RLR family. RIG-I is a key PRR for the detection of positive-and negative-stranded RNA viruses in the cytoplasm of cells 6,7 , and plays an important role in triggering responses against many viruses, such as orthomyxovirus (influenza A virus) and paramyxovirus (measles, mumps, and Sendai virus (SeV)) families, hepatitis C virus (HCV), and Japanese encephalitis virus (JEV) 8 . 5'-triphosphate modifications of RNA (3pRNA) are essential for RIG-I recognition and activation 9,10 . Ligand-binding activates the ATPase activity of RIG-I to change its structural conformation 6 , which in turn enables RIG-I to interact through its N-terminal tandem caspase recruitment domain (CARD) with the adaptor protein MAVS (for mitochondrial antiviral signaling protein, also known as IPS-1, VISA, or Cardif) [11][12][13][14] . MAVS then initiates the activation of interferon (IFN)-regulatory factor (IRF) 3, IRF7 and NF-κB transcriptional pathways for the subsequent production of type I IFNs and inflammatory cytokines, which are crucial for activating innate immune responses to viral infection 6,15 . Given the important role of the RIG-I pathway in the antiviral innate response, the mechanisms regulating RIG-I activation represent a topic of intense research [16][17][18] .Poly(ADP-ribose) polymerases (PARPs), a superfamily with least 17 members, are known to regulate not only cell survival and cell death programs triggered by DNA 3 damage, but also other biological functions as well as pathological processes, such as inflammatory and degenerative diseases, in a manner dependent or independent of their PARP activity [19][20][21][22] . Several PARP-superfamily members have a direct regulatory effect on replication of certain viruses 19,20,22,23 RESULTS 4PARPs contribute to the IFN response To investigate the role of the PARP-superfamily members in nucleic acid induced innate immune responses, we selected some of the PARP-superfamily members known to be involved in microbial infection, inflammation and immunity: PARP-1, PARP-2, PARP-7, PARP-9, 23,[31][32][33][34]. We then examined whether they have the ability to enhance the induction of IFNB mRNA in HEK293T cells in response to stimulation with three different types of nucleic acids-3pRNA, poly(rI:rC) and poly(dA-dT)•poly(dA-dT) (named poly(dA:dT) hereafter).Among the protein tested, PARP-13 uniquely showed a marked enhancing effect on IFNB mRNA expression induced by stimulation with 3pRNA, poly(rI:rC) and poly(dA:dT) ( Fig. 1a), all of which are known to activate the RIG-I-mediated pathway in HEK293T cells 9,10,[35][36][37] . A weak increase in IFNB mRNA expression was also detected in cells expressing PARP-1, PARP-2 and PARP-9. PARP-13 exists in at least two isoforms 22,26,38 . The amino-terminal 254-amino acid fragment of the rat homologue, which corresponds to the N...

The antioncogenic Chk2 kinase plays a crucial role in DNA damage-induced cell-cycle checkpoint regulation. Here we show that Chk2 associates with the oncogenic protein Wip1 (wild-type p53-inducible phosphatase 1) (PPM1D), a p53-inducible protein phosphatase. Phosphorylation of Chk2 at threonine68 (Thr68), a critical event for Chk2 activation, which is normally induced by DNA damage or overexpression of Chk2, is inhibited by expression of wild-type (WT), but not a phosphatase-deficient mutant (D314A) of Wip1 in cultured cells. Furthermore, an in vitro phosphatase assay revealed that Wip1 (WT), but not Wip1 (D314A), dephosphorylates Thr68 on phosphorylated Chk2 in vitro, resulting in the inhibition of Chk2 kinase activity toward glutathione S-transferase-Cdc25C. Moreover, inhibition of Wip1 expression by RNA interference results in abnormally sustained Thr68 phosphorylation of Chk2 and increased susceptibility of cells in response to DNA damage, indicating that Wip1 acts as a negative regulator of Chk2 in response to DNA damage.

Disrupted hematopoiesis and delayed immune reconstitution are life-threatening complications of allogeneic hematopoietic stem cell transplantation (allo-HSCT). Although graft-versus-host disease (GVHD) is a major risk factor for the bone marrow (BM) insufficiency, how GVHD impairs BM hematopoiesis has been largely unknown. We hypothesized that BM stromal niche could be a target of GVHD. In major histocompatibility complex (

Reactivation of resolved hepatitis B virus (HBV) infection, which is known as reverse seroconversion (RS), has been reported as a rare complication of allogeneic hematopoietic stem cell transplantation. We retrospectively studied HBV serologic markers in 14 recipients with pretransplant anti-hepatitis B surface antigen antibody (anti-HBs). Progressive decreases in anti-HBs titer were observed in all cases. In 12 cases, anti-HBs titer had decreased to under the protective value. RS occurred in seven cases after disappearance of anti-HBs. Although reseroconversion occurred in five cases, two cases remained in an HBV-carrier status after resolution of hepatitis. In the other five cases, RS did not occur even after disappearance of anti-HBs. The actual risks of anti-HBs disappearance and RS were estimated to be 75.0% and 39.8% at 2 years and 100.0% and 70.0% at 5 years, respectively. In conclusion, RS is a late-onset complication with high frequency that can be predicted by careful monitoring of progressive decrease in anti-HBs titer.

The reported outcome of hematopoietic stem cell transplantation (HSCT) from HLA-mismatched family members has been inconsistent. The object of this study was to evaluate the true impact of HLAmismatch by using recent data from a homogenous population, excluding HSCT procedures that used graft manipulations, and by considering genotypic matching. Clinical data of 2947 patients who underwent allogeneic HSCT for leukemia or myelodysplastic syndrome were extracted from the database of the Japan Society for Hematopoietic Cell Transplantation. The main outcome measures were survival and the incidence of graft-versushost disease (GVHD). The presence of serologic HLA-mismatch, higher age, and high-risk disease were identified as independent risk factors for both shorter survival and the development of grade III to IV acute GVHD. The impact of HLAmismatch on survival was more relevant in standard-risk patients. These findings persisted when we used genotypic HLA matching. Survival after one-locusmismatched HSCT was equivalent to that after HLA-matched unrelated HSCT. We concluded that when a one-locusmismatched family donor is available for high-risk patients, immediate HSCT using this donor is warranted. In standard-risk patients, however, survival after onelocus-mismatched HSCT is significantly shorter than that after HLA-matched HSCT, and the indications for HSCT should be considered carefully. (Blood. 2003;102:1541-1547)