绿草履虫Parameciumbursaria大核染色质组份和组蛋白的研究

绿草履虫P.bursaria是在接有产气杆菌Aerobacter aerogenes的无菌稻草提取液中进行克隆培养后取得的.在非离子去污剂NP-40(含有二价阳离子Ca~(2+),Mg~(2+))的溶液中裂解细胞,经蔗糖梯度离心分离、提纯细胞大核,并制备染色质,测定其中组蛋白、非组蛋白、DNA和RNA的相对含量.用稀酸抽提绿草履虫大核和大核染色质,得到的酸溶性蛋白(即组蛋白),经PAGE、SDS-PAGE、PAGIF和氨基酸分析等方法测定.得到的结果是:绿草履虫大核染色质中DNA:RNA∶组蛋白∶非组蛋白=1∶0.02∶1.30∶0.59;组蛋白占染色质蛋白质的68.8%;大核和大核染色质的酸溶性蛋白是相同的,都具有相当于高等动物的全组蛋白的五条组蛋白带,只在其相对含量及电泳迁移率上,与高等动物的全组蛋白略有差别;由16种氨基酸组成,20%是酸性氨基酸,不存在色氨酸和半胱氨酸;五条蛋白带的分子量为11000～21000道尔顿,也类似于哺乳动物细胞组蛋白;这是一类碱性很弱的蛋白质,等电点为pH 8.02～9.4;碱性氨基酸和酸性氨基酸的比为1.03∶1,这一点却更接近酵母全组蛋白.     

p53-dependent upregulation of PIG3 transcription by γ-ray irradiation and its interaction with KAP1 in responding to DNA damage

PIG3 (p53-inducible gene 3), originally identified as one of a set of genes induced by p53 before the onset of apoptosis, was assumed to contribute to early cellular response to DNA damage. Here, we studied the relation between p53 status and the increased expression of PIG3 by ionizing radiation (IR), and the related clues regarding the involvement of PIG3 in the cellular response to IR-induced DNA damage signaling. We demonstrated that the pentanucleotide microsatellite sequence was responsible for the p5...     

原生动物四膜虫(TetrahymenaS1)高迁移率非组蛋白的研究

利用原生动物四膜虫(TetrahymenashanghaiensisS1)作材料,经高氯酸抽提,丙酮沉淀等方法,制备取得高迁移率的非组蛋白。在高分辨率的乙酸一脲电泳图谱上,具有小牛胸腺所具有的典型的全部蛋白带。此外还含有一些未经检测的蛋白带。作者认为这些多余蛋白带可能是四膜虫所特有的高迁移率的非组蛋白。     

核仁抗原在白血病诊断中的初步观察

用抗核仁抗原NAg-1的抗血清对各种白血病人骨髓组织进行免疫荧光染色.结果表明,急性白血病患者的NAg-1阳性细胞率显著高于正常人及各种非白血病贫血患者.在处于完全缓解的白血病患者中,具有较高的NAg-1阳性率者(>10％)比较低者(<10％)更易复发.     

几种动物间期核染色质的电镜研究

用电镜对不同种动物细胞间期核染色质进行了研究,结果表明染色质在间期核内有不同结构层次。其中主要是直径为２０－３０ｎｍ纤维,也有较多１０ｎｍ纤维,不同咱动物间期核染色质的存在形式和排布有一定差异。赤链蛇肝细胞间期核没有聚集的异染色质区,整个核内均匀分布着直径为２０ｎｍ的纤维。     

Emerging connections between DNA methylation and histone acetylation

Modifications of both DNA and chromatin can affect gene expression and lead to gene silencing. Evidence of links between DNA methylation and histone hypoacetylation is accumulating. Several proteins that specifically bind to methylated DNA are associated with complexes that include histone deacetylases (HDACs). In addition, DNA methyltransferases of mammals appear to interact with HDACs. Experiments with animal cells have shown that HDACs are responsible for part of the repressive effect of DNA methylation. Evidence was found in Neurospora that protein acetylation can in some cases affect DNA methylation. The available data suggest that the roles of DNA methylation and histone hypoacetylation, and their relationship with each other, can vary, even within an organism. Some open questions in this emerging field that should be answered in the near future are discussed.     

Chromatin assembly during S phase: contributions from histone deposition, DNA replication and the cell division cycle

During S phase of the eukaryotic cell division cycle, newly replicated DNA is rapidly assembled into chromatin. Newly synthesised histones form complexes with chromatin assembly factors, mediating their deposition onto nascent DNA and their assembly into nucleosomes. Chromatin assembly factor 1, CAF-1, is a specialised assembly factor that targets these histones to replicating DNA by association with the replication fork associated protein, proliferating cell nuclear antigen, PCNA. Nucleosomes are further organised into ordered arrays along the DNA by the activity of ATP-dependent chromatin assembly and spacing factors such as ATP-utilising chromatin assembly and remodelling factor ACF. An additional level of controlling chromatin assembly pathways has become apparent by the observation of functional requirements for cyclin-dependent protein kinases, casein kinase II and protein phosphatases. In this review, we will discuss replication-associated histone deposition and nucleosome assembly pathways, and we will focus in particular on how nucleosome assembly is linked to DNA replication and how it may be regulated by the cell cycle control machinery.     

Integrase, LEDGF/p75 and HIV replication

HIV integrates a DNA copy of its genome into a host cell chromosome in each replication cycle. The essential DNA cleaving and joining chemistry of integration is known, but there is less understanding of the process as it occurs in a cell, where two complex and dynamic macromolecular entities are joined: the viral pre-integration complex and chromatin. Among implicated cellular factors, much recent attention has coalesced around LEDGF/p75, a nuclear protein that may act as a chromatin docking factor or receptor for lentiviral pre-integration complexes. LEDGF/p75 tethers HIV integrase to chromatin, protects it from degradation, and strongly influences the genome-wide pattern of HIV integration. Depleting the protein from cells and/or over-expressing its integrase-binding domain blocks viral replication. Current goals are to establish the underlying mechanisms and to determine whether this knowledge can be exploited for antiviral therapy or for targeting lentiviral vector integration in human gene therapy. Received 25 November 2007; received after revision 7 January 2008; accepted 10 January 2008