The severe acute respiratory syndrome coronavirus (SARS-CoV) is the major causative agent for the worldwide outbreak of SARS in 2003. The mechanism by which SARS-CoV causes atypical pneumonia remains unclear. The nuclear factor kappa B (NF-κB) is a key transcription factor that activates numerous genes involved in cellular immune response and inflammation. Many studies have shown that NF-κB plays an important role in the pathogenesis of lung diseases. In this study, we investigated the possible regulatory interaction between the SARS-CoV nucleocapsid (N) protein and NF-κB by luciferase activity assay. Our results showed that the SARS-CoV N protein can significantly activate NF-κB only in Vero E6 cells, which are susceptible to SARS-CoV infection, but not in Vero or HeLa cells. This suggests that NF-κB activation is cell-specific. Furthermore, NF-κB activation in Vero E6 cells expressing the N protein is dosedependent. Further experiments showed that there is more than one function domain in the N protein responsible for NF-κB activation. Our data indicated the possible role of the N protein in the pathogenesis of SARS.

T4病毒科由一类单股正链RNA病毒组成，分为松天蛾B样病毒属和松天蛾 样病毒属。这2个属的病毒具有不同的基因组结构，8样病毒含单组分基因组，其结构蛋白由一亚基因组RNA表达；而 样病毒含双组分基因组，2个RNA分子分别编码复制酶蛋白和结构蛋白。在T4病毒基因组RNA3 端有类似tRNA的二级结构。样病毒壳蛋白的氨基酸序列一致性高达66%～86&，而G样病毒壳蛋白的氨基酸同源性则要低得多。在昆虫细胞中表达壳蛋白基因时都能形成病毒类似粒子。该文还介绍了T4病毒复制机理以及T4病毒与其他病毒的进化关系。

为了表达马尾松毛虫质型多角体病毒（DpCPV）多角体蛋白基因（s10片段）并探讨多角体蛋白在真核细胞中的定位，从DpCPV中分离出S10， pET-28a载体连接成重组表达质粒pET28-SIO；将sl0克隆到杆状病毒转座载体pFASTBAC HTb中，依次筛选出重组转座质粒pFASTBAC S10，重组穿梭质粒Bacmid S10，重组杆状病毒Ac Sl0。多角体蛋自基 表达后，刚SDS. PAGE、Western. blot和免疫荧光技术对表达产物进行了检测。结果表明：Sl0原核表达质粒、重组杆状病毒成功获得；在昆虫细胞中表达的质型多角体蛋白主要定位于细胞质，同时有少量产物定位f细胞核。

用Trizol从纯化的茶尺蠖Ectropis oblique小RNA病毒（EoPV）中提取病毒基因组RNA，逆转录后加poly（dT），然后进行两步PCR扩增基因组5'端。克隆测序后，对其5 端非编码区的核苷酸序列进行分析，发现具有哺乳动物小RNA病毒的5'端非编码区的一些特征：A/T含量丰富、起始密码子上游AUG和小顺反子多。利用mfold预测了EoPV5'端非编码区的二级结构，存在4个茎环结构，有哺乳动物内部核糖体进入位点（IRES）的保守区域，即含保守基序GNRA的茎环A和A/C丰富的环B及多聚嘧啶区域。据此推测EoPV基因组翻译采用IRES起始机制。

The non-structural (NS) proteins of parvoviruses are involved in essential steps of the viral life cycle. Various biochemical functions, such as ATP binding, ATPase, site-specific DNA binding and nicking, and helicase activities, have been assigned to the protein NS1. Compared with the non-structural proteins of the vertebrate parvoviruses, the NS proteins of the Densovirinae have not been well characterized. Here, we describe the biochemical properties of NS1 of Periplaneta fuliginosa densovirus (PfDNV). We have expressed and purified NS1 using a baculovirus system and analyzed its enzymatic activity. The purified recombinant NS1 protein possesses ATPaseand ATP-or dATP-dependent helicase activity requiring either Mg2+ or Mn2+ as a cofactor. The ATPase activity of NS1 can be efficiently stimulated by single-stranded DNA. The ATPase coupled helicase activity was detected on blunt-ended double-stranded oligonucleotide substrate. Using South-Western and Dot-spot assays, we identified a DNA fragment that is recognized specifically by the recombinant NS1 protein. The fragment consists of (CAC)4 and is located on the hairpin region of the terminal palindrome. The domain for DNA binding was defined to the amino-terminal region (amino acids 1-250). In addition, we found that NS1 can form oligomeric complexes in vivo and in vitro. Mutagenesis analysis showed that ATP binding is necessary for oligomerization. Based on these results, it seems that PfDNV NS1, a multifunctional protein, plays an important role in viral DNA replication comparable to those of vertebrate parvovirus initiator proteins.

The nucleotide sequence of a novel icosahedral DNA virus infecting Dendrolimus punctatus has been determined. The genome is 5039 nt long and includes inverted terminal repeats of 200 nt containing 131 nt long J-shaped terminal hairpins. The 'plus' strand of the genome contains three large open reading frames (ORFs), the left and the mid-ORFs (within the left ORF) in the left-half encoding the non-structural proteins and the right ORF in the right-half encoding viral capsid proteins. NS1 protein contains conserved replication initiation and DNA-dependent ATPase/helicase domains. VP1 protein contains a conserved PGY and phospholipase A2 motifs and shows high identities with VPs of Casphalia extranea densovirus and Bombyx mori densovirus-1 belonging to the genus Iteravirus. Phylogenetic analysis also revealed that this virus is most closely related to Casphalia extranea densovirus and Bombyx mori densovirus-1. Consequently, this virus was considered as a new third member of the genus Iteravirus of the subfamily Densovirinae, and designated Dendrolimus punctatus densovirus.

The complete nucleotide sequence of a new insect picorna-like virus, Ectropis obliqua picorna-like virus (EoPV), which causes a fatal infection of Ectropis obliqua larvae, has been determined. The genomic RNA of EoPV is 9394 nt in length and contains a single, large open reading frame (nt 391-9351) encoding a polyprotein of 2987 aa. Sequence comparisons with other viral polyproteins revealed that the consensus sequences for picornavirus RNA helicase, protease and RNA-dependent RNA polymerase proteins are found on the genome in order in the 59R39 direction. All structural genes were located at the 59 terminus. In terms of sequence similarity, identity and genome organization, EoPV resembles mammalian picornaviruses and three other insect picorna-like viruses: Infectious flacherie virus of silkworm, Sacbrood virus of honeybee and Perina nuda picorna-like virus (PnPV). Phylogenetic analysis showed that EoPV is most closely related to PnPV and suggests that these four insect picorna-like viruses might constitute a new group of insect-infectious RNA viruses.

In this study, Dendrolimus punctatus tetravirus (DpTV) has been identified as a new member of the genus Omegatetravirus of the family Tetraviridae that may be related serologically to Nudaurelia capensis v virus (NvV). DpTV particles are isometric, with a diameter of about 40nm and a buoyant density of 1?281 g cm3 in CsCl. The virus has two capsid proteins (of 62 500 and 6800 Da) and two single-stranded RNA molecules (RNA1 and RNA2), which are 5492 and 2490 nt long, respectively. RNA1 has a large open reading frame (ORF) encoding a polypeptide of 180 kDa; RNA2 contains two partially overlapping ORFs encoding polypeptides of 17 and 70 kDa. The 180 kDa protein, which contains consensus motifs of a putative methyltransferase, helicase and RNA-dependent RNA polymerase, shows significant similarity to those of other tetraviruses. The 17 kDa protein is a PEST (Pro/Glu/Ser/Thr) protein of unknown function. The 70 kDa protein is the coat protein precursor and is predicted to be cleaved at an Asn-Phe site located after residue 570. The 70 kDa protein shows 86 and 66% identity to its homologues in NvV and Helicoverpa armigera stunt virus, respectively. Secondary-structure analysis revealed that the RNAs of DpTV have tRNA-like structures at their 39 termini.

We examined the intracellular localization of NS5 protein of Dendrolimus punctatus cytoplasmic polyhedrosis virus (DpCPV) by expressing NS5-GFP fusion protein and proteins from deletion mutants of NS5 in baculovirus recombinant infected insect Spodoptera frugiperda (Sf-9) cells. It was found that the NS5 protein was present at the plasma membrane of the cells, and that the N-terminal portion of the protein played a key role in the localization. A transmembrane region was identified to be present in the N-terminal portion of the protein, and the detailed transmembrane domain (SQIHMVWVKSGLVFF, 57-71aa) of N-terminal portion of NS5 was further determined, which was accorded with the predicted results, these findings suggested that NS5 might have an important function in viral life cycle.