用单抗5C5和5C5—G1筛选的613bp cDNA的核苷酸序列分析

用识别人活化Ｂ细胞分化抗原５Ｃ５的单克隆抗体５Ｃ５和５Ｃ５－Ｇ１的混合物从人扁桃体细胞λｇｔ１１ ｃＤＮＡ文库筛选到３个阳性克隆。其ｃＤＮＡ插入到质粒ｐＵＣ１８，经双链双脱氧测序法作核苷酸序列分析，知其中一个ｃＤＮＡ长６１３ｂｐ，另二个长４６７ｂｐ，后者与前者的前４６７ｂｐ完全重叠。６１３ｂｐ ｃＤＮＡ中有一个开放阅读框架，从１０３ｂｐ到４２９ｂｐ，共３２７ｂｐ。Ｎｏｒｔｈｅｒｎ印迹分析显示，此６     

Genomic organization of Trypanosoma brucei variant antigen gene families in sequential parasitemias

cDNA libraries were made from mRNA purified from each of seven sequentially isolated variant antigen types (VATs) of the IsTat 1 serodeme. Plasmids containing variant surface glycoprotein (VSG) sequences corresponding to each of the isolates were used in Southern analyses to examine the genomic organization of VSG nucleotide sequences. In most cases, cells expressing a given VSG were shown to have an extra copy of the corresponding VSG gene. In one case an expression-linked copy (ELC) was not detectable. VSG gene rearrangements not obviously correlated with the expression of homologous sequences were detected in four of six VSG gene families. Thus, even cDNAs which detected an ELC revealed additional genomic reorganization in regions flanking VSG sequences. The cells used to initiate the chronic infection expressed the same VSG as those isolated from the first parasitemia. The extent of genomic rearrangement observed between these two sequentially derived populations was comparable to that observed between any of the other serially derived VATs. Thus, within a short period of time and in the absence of detectable antigenic variation, the amount of genetic flux in sequences associated with VSG genes can be substantial.     

Ionizing-radiation induced DNA double-strand breaks: A direct and indirect lighting up

The occurrence of DNA double-strand breaks (DSBs) induced by ionizing radiation has been extensively studied by biochemical or cell imaging techniques. Cell imaging development relies on technical advances as well as our knowledge of the cell DNA damage response (DDR) process. The DDR involves a complex network of proteins that initiate and coordinate DNA damage signaling and repair activities. As some DDR proteins assemble at DSBs in an established spatio-temporal pattern, visible nuclear foci are produced. In addition, post-translational modifications are important for the signaling and the recruitment of specific partners at damaged chromatin foci. We briefly review here the most widely used methods to study DSBs. We also discuss the development of indirect methods, using reporter expression or intra-nuclear antibodies, to follow the production of DSBs in real time and in living cells.     

The tripartite capsid gene of Salmonella phage Gifsy-2 yields a capsid assembly pathway engaging features from HK97 and λ

Phage Gifsy-2, a lambdoid phage infecting Salmonella, has an unusually large composite gene coding for its major capsid protein (mcp) at the C-terminal end, a ClpP-like protease at the N-terminus, and a ∼ 200 residue central domain of unknown function but which may have a scaffolding role. This combination of functions on a single coding region is more extensive than those observed in other phages such as HK97 (scaffold-capsid fusion) and λ (protease-scaffold fusion). To study the structural phenotype of the unique Gifsy-2 capsid gene, we have purified Gifsy-2 particles and visualized capsids and procapsids by cryoelectron microscopy, determining structures to resolutions up to 12 Å. The capsids have lambdoid T = 7 geometry and are well modeled with the atomic structures of HK97 mcp and phage λ gpD decoration protein. Thus, the unique Gifsy-2 capsid protein gene yields a capsid maturation pathway engaging features from both phages HK97 and λ.     

Lack of association between CTLA-4 and PDCD1 polymorphisms and acute rejection in German liver transplant recipients

Cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) and programmed cell-death 1 (PDCD1) are two genes encoding coinhibitory immunoreceptors that are involved in regulation transplant rejection and tolerance induction. Thus, CTLA-4 and PDCD1 may be good candidate genes to evaluate in liver transplant rejection. In this retrospective study, we investigated whether four functional single nucleotide polymorphisms (SNP) of the CTLA-4 gene and PDCD1 gene were associated with susceptibility to liver transplant rejection. The SNPs −1772T > C (rs733618), −1661A > G (rs4553808) of the CTLA-4 gene, and the SNPs 7146G > A (rs11568821), 7209C > T (rs41386349) of the PDCD1 gene were genotyped by polymerase chain reaction allele specific restriction enzyme analysis (PCR-ASRA) in 100 liver recipients with acute rejection, 104 liver transplant recipients without acute rejection and 100 healthy control individuals. For the selected SNPs we did not detect any significant difference in genotypic and allelic frequencies between liver transplant recipients with and without acute rejection. In conclusion, our results suggest that the tested SNPs may not be associated with susceptibility to acute liver transplant rejection in a Caucasian population.     

白细胞抗原G基因14bp插入缺失多态与丙型肝炎病毒慢性感染的关联

目的：研究人类白细胞抗原G（HLA-G）基因14 bp插入缺失多态与丙型肝炎病毒（hepatitis C virus,HCV）慢性感染的相关性.方法：选取HCV慢性感染者243例（感染组）,无血缘关系的汉族健康对照448例（HCV对照组）.采用PCR序列特异引物法检测HLA-G基因第8外显子3＇UTR的1个14 bp插入缺失多态,并比较其在HCV慢性感染人群和健康人群中的分布情况.结果：HLA-G基因14 bp插入等位基因频率在对照组中为0.335,在HCV感染组中为0.348;14 bp插入纯合子基因型频率在对照组中为0.112,在HCV感染组中为0.107.无论是基因型频率还是等位基因频率,在HCV感染组和对照组中均无统计学差异.结论：HLA-G基因14 bp插入缺失多态性与汉族人群中HCV感染的发生无遗传易感染性关联.