The immunoglobulin mu constant region gene is expressed in mouse thymocytes

It has been a matter of controversy whether the functional capacity of T cells to discriminate between antigens is mediated via immunoglobulin, an immunoglobulin-like molecule, or by the product(s) of unrelated genes. The progenitors of immunoglobulin-secreting cells, B cells, express membrane-bound immunoglobulin as the antigen-specific receptor on their surface. For T cells, although products of immunoglobulin heavy chain variable region genes are implicated as receptor components, there has been no compelling immunochemical evidence for participation of either immunoglobulin light chains or heavy chain constant regions (see refs 2-6 for the disparate views). Recently, using cloned immunoglobulin DNA sequences as hybridization probes, we have demonstrated that the immunoglobulin Cmu gene, but not the Cmu gene, is expressed as polyadenylated RNA in some T cell tumour (T lymphoma) cell lines. Individual T lymphoma lines yielded up to three discrete mu RNA species of different sizes (1.9, 2.2 and 3.0 kilobases), each species being different in size from the major mu RNA species present in B lymphoma cells (2.4 and 2.7 kilobases). We show here that cells from the normal mouse thymus contain mu RNA species, indistinguishable in size from those in T lymphoma cells, but contain little if any kappa RNA.     

筛选p53靶向药物的细胞模型的构建

为了筛选可以恢复肿瘤细胞中p53功能的小分子,作者用表达野生型p53的人类直肠癌细胞HCT116建立了一株能够应答激活p53信号通路的荧光素酶报告基因的稳定细胞系,同时用表达野生型p53的人类骨肉瘤细胞U2-OS建立了一株能够应答激活p53信号通路的mCherry红色荧光蛋白报告基因的稳定细胞系.为了检测筛选p53靶向药物的有效性,利用三种已知的以p53为靶点的小分子药物(cisplatin,doxorubicin以及Nutlin-3)处理这两种稳定细胞系,结果显示p53信号通路在这两个稳定细胞系中均能够被激活.为了探索小分子RNA作为恢复p53功能的靶标药物,并进一步验证这两种细胞模型用于药物筛选的可行性,分别检测了MDM2和MDMX的5个不同shRNA.通过比较HCT116稳定细胞的荧光素酶活性和U2-OS稳定细胞中荧光蛋白的荧光强度,我们筛选出了有效沉默MDM2或MDMX的shRNA.数据表明,这两种细胞模型不仅可用作筛选激活p53的小分子化合物的平台,而且可用于筛选激活p53信号通路的小分子RNA.     

An in vivo recombinant RNA capable of autocatalytic synthesis by Q beta replicase

A variety of small RNAs ranging from tens to hundreds of nucleotides in length grow autocatalytically in a Q beta replicase (Q beta phage RNA-dependent RNA polymerase) reaction in the absence of added template, and similar RNAs are found in Q beta phage-infected Escherichia coli cells. Three such RNAs have been sequenced. One of them that is 221 nucleotides (nt) long ('MDV-1' RNA) has been found to be partially homologous to Q beta phage RNA 8, which might be considered as an indication of its origination from by-products of the Q beta RNA replication. To gain further insight into the origin and function of these RNAs, we have sequenced a new RNA, 120 nt long, isolated from the products of spontaneous synthesis by the nominally RNA-free Q beta replicase preparation. The minus strand of this RNA appeared to be a recombinant RNA, composed of the internal fragment of Q beta RNA (approximately 80 nt long) and the 33-nt-long 3'-terminal fragment of E. coli tRNA(1Asp). This seems to be the first strong indication of RNA recombination in bacterial cells. The various implications of this finding are discussed.     

具全期启动子盒的杆状病毒高效表达载体的组建与应用

通过ＰＣＲ扩增，得到苜蓿丫纹夜蛾核型多角体病毒（ＡｕｔｏｇｒａｐｈａｃａｌｉｆｏｒｎｉｃａＮｕｃｌｅａｒＰｏｌｙｈｅｄｒｏｓｉｓＶｉｒｕｓ，ＡｃＮＰＶ）具早晚期启动子元件的ｐ３５基因启动子，将其插入到杆状病毒转移载体质粒ｐＳＸＩＶＶＩ＋Ｘ３多克隆位点上游，使之与ｐＳＸＩＶＶＩ＋Ｘ３质粒中的人工合成后期启动子（ＰＳｙｎ）、多角体ＸＩＶ启动子（ＰＸＩＶ）串联构成早期、晚期、极晚期能持续启动外源基因表达的转移载体质粒ｐＳＸ３５．将ｐＳＸ３５用于组建含ＨＢｓＡｇ基因并形成多角体的重组ＴｎＮＰＶ，ＨＢ－ｓＡｇ基因的表达量显著提高，表达时间亦明显提前，从而实现了外源基因在杆状病毒表达系统的全期、高效表达．ｍＲＮＡ引物延伸试验结果显示，Ｐｐ３５在重组病毒中可产生２套转录本，分别于病毒感染的早期和晚期起始ＨＢｓＡｇ基因的表达．     

Expression and anti-apoptoticmechanism of Spodoptera lit-toralis NucleopolyhedrovirusP49 protein

A novel cloned Spodoptera littoralis Nucleopolyhedrovirus (SlNPV) p49 gene is able to suppress apoptosis of insect cells Sf9 triggered by virus. The amino acid sequence of P49 expressed in baculovirus expression system is the same as predicted, indicating that the expression of P49 is correct. Metabolic labeling revealed that p49 was able to be expressed both in the early and late phases after the viral infection, and only in the late phase was the expression driven by polyhedra promoter, but the amount of expression was higher than that of wtSlNPV. In summary, the early gene of SlNPV p49 as well as p35 of AcMNPV is able to be expressed in the late phase, but its promoter is weaker compared with polyhedra promoter. In vitro, P49 can be cut by Bm caspase and human caspase-3, yielding 10 and 40 ku fragments. Purified P49 blocks the substrate cleavage by Bm caspase and human caspase-3, showing that P49 inhibits downstream caspases in the apoptotic pathway.