Molecular structure and biological function of proliferating cell nuclear antigen

Proliferating cell nuclear antigen (PCNA) is the core component of replication complex in eukaryote. As a processive factor of DNA polymerase delta, PCNA coordinates the replication process by interacting with various replication proteins. PCNA appears to play an essential role in many cell events, such as DNA damage repair, cell cycle regulation, and apoptosis, through the coordination or organization of different partners. PCNA is an essential factor in cell proliferation, and has clinical significance in tumor research. In this article we review the functional structure of PCNA, which acts as a function switch in different cell events.     

Identity of the proliferating cell nuclear antigen and cyclin

Studies of growth regulation and cellular transformation will be assisted by the identification of proteins that are preferentially synthesized in dividing cells. The 'proliferating cell nuclear antigen' ( PCNA ), distinguished by its apparent association with cell division, is defined by reaction with an antibody found in the autoimmune disease systemic lupus erythematosus (SLE). This antibody reacts with proliferating cells including tumour cells but gives weak or undetectable immunofluorescence with resting cells of normal tissues. Peripheral blood lymphocytes are devoid of PCNA until activated by mitogen in vitro. In synchronized cultures its level and distribution fluctuate through the cell cycle, with a striking accumulation in the nucleolus late in the G1 phase and early in the S phase. Many of these properties are shared by ' cyclin '. This nuclear protein, identified by its position in a two-dimensional separation of cell proteins, is also transformation-sensitive and is preferentially synthesized in the S phase. We establish here that PCNA and cyclin are identical, and show that PCNA is an acidic nuclear protein of apparent molecular weight 35,000.     

Functional identity of proliferating cell nuclear antigen and a DNA polymerase-delta auxiliary protein

The mechanism of replication of the simian virus 40 (SV40) genome closely resembles that of cellular chromosomes, thereby providing an excellent model system for examining the enzymatic requirements for DNA replication. Only one viral gene product, the large tumour antigen (large-T antigen), is required for viral replication, so the majority of replication enzymes must be cellular. Indeed, a number of enzymatic activities associated with replication and the S phase of the cell cycle are induced upon SV40 infection. Cell-free extracts derived from human cells, when supplemented with immunopurified SV40 large-T antigen support efficient replication of plasmids that contain the SV40 origin of DNA replication. Using this system, a cellular protein of relative molecular mass 36,000 (Mr = 36K) that is required for the elongation stage of SV40 DNA replication in vitro has been purified and identified as a known cell-cycle regulated protein, alternatively called the proliferating cell nuclear antigen (PCNA) or cyclin. It was noticed that, in its physical characteristics, PCNA closely resembles a protein that regulates the activity of calf thymus DNA polymerase-delta. Here we show that PCNA and the polymerase-delta auxiliary protein have similar electrophoretic behaviour and are both recognized by anti-PCNA human autoantibodies. More importantly, both proteins are functionally equivalent; they stimulate SV40 DNA replication in vitro and increase the processivity of calf thymus DNA polymerase-delta. These results implicate a novel animal cell DNA polymerase, DNA polymerase-delta, in the elongation stage of replicative DNA synthesis in vitro.     

幽门螺杆菌培养滤波对IL-8及胃粘膜增殖细胞核抗原表达的影响

目的:研究幽门螺杆菌(Helicobacter pylori,Hp)代谢产物对炎性细胞因子白细胞介素8(interleukin-8,IL-8)表达的影响以及在胃粘膜上皮细胞增殖中的作用。方法:用CagA阳性Hp培养滤液给大鼠灌胃,2周后,采用ELISA法检测鼠血清中的IL-8水平,免疫组织化学SP(streptavidin/perosidase)法检测胃粘膜增殖细胞核抗原(proliferation cell nuclear antigen,PCNA)的表达。结果:灌服Hp滤液组与对照组比较,血清IL-8升高,胃粘膜PCNA标记指数阳性率升高,均有显著性意义。结论:CagA阳性Hp培养滤液可促进炎性因子IL-8的表达,促进胃粘膜上皮细胞的增殖,可能促进胃癌的发生。     

Comprehensive diagnostic value of P53, p21WAF1 and proliferating cell nuclear antigen for lung cancer

The expression of P53, p21WAF1 and proliferating cell nuclear antigen (PCNA) was detected in 114 samples of lung cancer patients (with 89 cases benign lung tissue as control) and the diagnostic value of these markers was evaluated. The results show the following: ➀ The positive expression rates of P53, p21WAF1 and PCNA in samples of lung cancer were 47.37%, 75.44% and 80.70%, respectively, which were significantly higher than that in the samples of benign lung diseases ( p < 0.001). The odds ratios were 39.15, 5.75, and 6.76, respectively. This indicates that the expression of P53, p21WAF1 and PCNA was helpful for the diagnosis of lung cancer. ➁ For the diagnosis of lung cancer, the positive likelihood ratio of P53 was 21.08, which were significantly higher than that of p21WAF1 (2.16), PCNA (2.11) and of all the combined tests. This shows that P53 expression was the most valuable for diagnosis of lung cancer. ➂ For the diagnosis of lung cancer, the negative likelihood ratio of P53/p21WAF1/PCNA parallel test was 0.057 1, which was lower than that of other single and combined tests. This indicates that P53/p21WAF1/PCNA parallel test has high diagnostic value for exclusion of lung cancer.     

当归注射液对兔主动脉平滑肌细胞中增殖细胞核抗原表达的影响

目的：观察当归注射液对平滑肌细胞（ Ｓ Ｍ Ｃ） 中增殖细胞核抗原（ Ｐ Ｃ Ｎ Ａ） 表达的影响。方法：用免疫组织化学 Ｌ Ｓ Ａ Ｂ 法检测培养的兔主动脉 Ｓ Ｍ Ｃ 中 Ｐ Ｃ Ｎ Ａ 的表达,同时测定培养液中超氧化物歧化酶（ Ｓ Ｏ Ｄ） 、脂质过氧化物（ Ｌ Ｐ Ｏ） 、前列环素（ Ｐ Ｇ Ｉ２） 及环磷酸腺苷（ｃ Ａ Ｍ Ｐ） 的含量。结果：当归注射液能增加 Ｓ Ｏ Ｄ 活性,降低 Ｌ Ｐ Ｏ 和升高 Ｐ Ｇ Ｉ２ 、ｃ Ａ Ｍ Ｐ 水平,抑制 Ｓ Ｍ Ｃ 中 Ｐ Ｃ Ｎ Ａ 的表达（ Ｐ＜ ００５ ～００１） 。结论：当归有抑制 Ｓ Ｍ Ｃ 增殖的作用。     

分子生物学技术及其在环境样品微生物分析中的应用

综述了荧光原位杂交(FISH)、多聚酶链式反应(PCR)、DNA克隆及DNA测序等分子生物学技术,并将这些分子生物学技术应用到淡水水体底泥厌氧氨氧化茵(anammox菌)和好氧氨氧化菌的原位检测中,从底泥样品中鉴别出这两种细菌,其中好氧氨氧化菌属于亚硝酸单胞菌属,厌氧氨氧化菌属于anammox菌的Brocadia分支,为进一步研究淡水环境中氮的微生物循环过程提供了一定的依据．     

DNA methylation status of H19 and Xist genes in lungs of somatic cell nuclear transfer bovines

In somatic cell nuclear transfer (SCNT) technologies,the donor cell’s nuclei need to be epigenetically reprogrammed for embryonic development. The incomplete reprogramming of donor cell nuclei has been implicated as a primary reason for the low efficiency of SCNT. DNA methylation is a major epige-netic modification of the genome that regulates crucial aspects of genome function,including estab-lishment of genomic imprinting. In order to make sure whether the DNA methylation reprogramming is efficient in SCNT animals,we analyzed the DNA methylation status of two imprinting genes,H19 and Xist,in lungs of deceased SCNT bovines that died within 48 h of birth using bisulfite sequencing analysis. Our findings demonstrated that cloned bovines showed significantly lower DNA methylation of H19 than controls (P<0.05),and three tested CpGs sites (1,2,3) exhibited unmethylation in one cloned bovine (9C3); however,Xist showed similar DNA methylation levels between clones and con-trols,and both showed hypermethylation (96.11% and 86.67%).     

Ni2B分子结构及成键特性的abinitio计算研究

本文用ＤＦＴ方法对Ｎｉ２Ｂ分子双重态和四重态两种多重度进行高水平的ａｂｉｎｉｔｉｏ计算，结果发现Ｂ以ｓｐ，ｓｐ＾２两种杂化方式同Ｎｉ成键，并且Ｂ带有相反的电荷；体系存在多个区域极小点。     

Effects of pH on structure and function of single living erythrocyte

The spontaneous changes in cell shape and size, the membrane bending elastic modulus, and the structure and functions of intracellular hemoglobin of single human living erythrocyte incubated in different suspension pH were studied. The non-invasive, in situ, real time measurements on the parameters at the three levels of intracellular molecule, membrane and cell morphology were performed simultaneously by using a fast micro-image analyzing technology and a multi-channel micro-spectrophotometer system. The result shows that the cell shape and size, the mechanical property of the cell membrane, and the structure and function of intracellular hemoglobin are correlated and affected by each other with pH.     

DNA methylation status of H19 and Xist genes in lungs of somatic cell nuclear transfer bovines

In somatic cell nuclear transfer （SCNT） technologies, the donor cell＇s nuclei need to be epigenetically reprogrsmmed for embryonic development. The incomplete reprogramming of donor cell nuclei has been Implicated as s primary reason for the low efficiency of SCNT. DNA methylstion is s major epigenetic modification of the genome that regulates crucial aspects of genome function, including establishment of genomic imprinting. In order to make sure whether the DNA methylstion reprogramming is efficient in SCNT animals, we analyzed the DNA methylstion status of two imprinting genes, H19 and Xist, in lungs of deceased SCNT bovines that died within 48 h of birth using bisulfite sequencing analysis. Our findings demonstrated that cloned bovines showed significantly lower DNA methylstion of H19 than controls （P〈0.05）, and three tested CpGs sites （1, 2, 3） exhibited unmethylstion in one cloned bovine （9C3）; however, Xist showed similar DNA methylation levels between clones and controis, and both showed hypermethylstion （96.11% and 86.67%）.