Transcriptional activation of histone subtypes is coordinately regulated and tightly coupled with the onset of DNA replication during S-phase entry. The underlying molecular mechanisms for such coordination and coupling are not well understood. The cyclin E-Cdk2 substrate NPAT has been shown to play an essential role in the transcriptional activation of histone genes at the G1/S-phase transition. Here, we show that NPAT interacts with components of the Tip60 histone acetyltransferase complex through a novel amino acid motif, which is functionally conserved in E2F and adenovirus E1A proteins. In addition, we demonstrate that transformation/transactivation domain-associated protein (TRRAP) and Tip60, two components of the Tip60 complex, associate with histone gene promoters at the G1/S-phase boundary in an NPAT-dependent manner. In correlation with the association of the TRRAP-Tip60 complex, histone H4 acetylation at histone gene promoters increases at the G1/S-phase transition, and this increase involves NPAT function. Suppression of TRRAP or Tip60 expression by RNA interference inhibits histone gene activation. Thus, our data support a model in which NPAT recruits the TRRAP-Tip60 complex to histone gene promoters to coordinate the transcriptional activation of multiple histone genes during the G1/S-phase transition.

Schistosome antigen-driven cytokine responses and antischistosome antibody levels of residents of a Schistosoma japonicum endemic island in Poyang Lake, Jiangxi Province were studied before and 45 days after treatment with praziquantel. IL-4, IL-5, IL-10 and INF-g were all detected in the supernatants of whole-blood cultures after stimulation with schistosome soluble egg antigen (SEA) and soluble worm antigen preparation (SWAP). The percentages of subjects producing detectable amounts of each cytokine assayed were higher in the group who were negative by stool examination at the start of the study than in those who were initially stool positive. After praziquantel treatment the percentages of subjects producing both type I and type II cytokines increased. This suggests that the production of both types of cytokine was down-regulated in the presence of live, egg-laying S. japonicum adult worms but that this was reversible by treatment. In contrast, the antibody studies showed higher levels of SWAP and SEA-specific antibodies (IgE, total IgG, IgG4, IgM) in subjects who were originally stoolpositive than in those who were stool-negative. After treatment specific IgE responses were elevated, but total IgG and IgG4 anti-SEA and IgM anti-SWAP antibody levels all fell significantly.

Activation of the G1 checkpoint following DNA damage leads to inhibition of cyclin E-Cdk2 and subsequent G1 arrest in higher eucaryotes. Little, however, is known about the molecular events downstream of cyclin E-Cdk2 inhibition. Here we show that, in addition to the inhibition of DNA synthesis, ionizing radiation induces downregulation of histone mRNA levels in mammalian cells. This downregulation occurs at the level of transcription and requires functional p53 and p21CIP1/WAF1 proteins. We demonstrate that DNA damage induced by ionizing radiation results in the suppression of phosphorylation of NPAT, an in vivo substrate of cyclin E-Cdk2 kinase and an essential regulator of histone gene transcription, and its dissociation from histone gene clusters in a p53/p21-dependent manner. Inhibition of Cdk2 activity by specific inhibitors in the absence of DNA damage similarly disperses NPAT from histone gene clusters and represses histone gene expression. Our results thus suggest that inhibition of Cdk2 activity following DNA damage results in the downregulation of histone gene transcription through dissociation of NPAT from histone gene clusters.

目的：探讨CD4+CD25+调节性T（Treg）细胞在慢性丙型肝炎患者免疫下调中的意义。方法：流式细胞仪检测慢性丙型肝炎患者外周血中CD4+CD25+Treg细胞的数量；与CD4+CD25-T细胞共同培养，检测其抑制功能；流式细胞仪检测其对CD4+CD25-T细胞合成IFN-γ和IL-4的影响；RTPCR检测CD4+CD25+Treg细胞中Foxp3的mRNA表达。结果：CD4+CD25+Treg细胞约占慢性丙型肝炎患者外周血中CD4+T细胞的14.1±1.6%，显著高于正常对照5.3±0.8%（P<0.01），显著抑制CD4+T细胞的增殖（P=0.002），以及合成IFN-γ。CD4+CD25+Treg细胞高表达Foxp3。结论：持续性HCV感染患者CD4+CD25+Treg细胞表达增加，特异性抑制Th1细胞反应。

目的：大量获得纯化的日本血吸虫22.6kDa重组抗原。方法：用PCR方法将其编码基因序列经改造后亚克隆入载体质粒pGEX-1λT进行表达。结果：得到了融合表达的蛋白抗原。此融合蛋白表达量大，用凝血酶酶切后易大量制备纯化的重组22.6kDa抗原。结论：以此融合蛋白免疫的小鼠抗血清进行免疫印迹试验，表明Sj22.6/Sj26GST融合重组蛋白具有与Sj22.6蛋白一样的免疫学活性。