Modulation of higher-order structure of F-factor DNA- protein complex and its partition function

1.F-因子DNA与sop基因产物的相互作用SOPA与DNA的相互作用：在SOP操纵子-启动子区域的四个SOPA结合位点被发现在抑制作用上几乎相同。获得了SOPA蛋白晶体。SopB与DNA的相互作用：表明SopB的基因沉默是由于蛋白质的高局部浓度导致非特异性DNA结合所致。II.寻找与宿主因子相互作用的SOP基因产物。SOPA相互作用蛋白：Far-Western分析显示有四种蛋白质与SOPA相互作用。经鉴定均为核糖体蛋白。SopB相互作用蛋白：可逆交联约70 KDa的蛋白质与SopB相互作用。发现了一种具有不寻常等电点的SopB小种。BrCN降解产物的MS分析表明，在蛋白质的两端附近发生了未知的修饰。III.染色体分离和DNA-蛋白质相互作用。参与染色体分离的蛋白质在细胞内的定位：人类DNA拓扑异构酶IIIβ被发现与处于M期的染色体相关。与参与染色体分离的蛋白质相互作用的蛋白质的特征：通过双杂交筛选分离的人DNAH同源物HSJ2的两个亚型作为诱饵的人拓扑异构酶IIIa在细胞内的分布。较长的基因产物定位于细胞核，而较短的基因产物在整个细胞内均匀分布。

I. Interaction between F-factor DNA and sop gene products.1. Interaction between SopA and DNA : Four SopA-binding sites in the sop operator-promoter region were found to be nearly equivalent in repression. Crystals of SopA protein were obtained.2. Interaction between SopB and DNA : It was indicated that gene silencing effected by SopB results from a high local concentration of the protein causing non-specific DNA binding.II. Search for host factors interaction sop gene products.1. SopA-interacting proteins : Far-Western analysis revealed four proteins interacting with SopA. All of them were identified as ribosomal proteins.2. SopB-interacting proteins : Reversible cross-linking revealed a ca. 70 KDa protein interacting with SopB. A minor species of SopB with an unusual pI was discovered. MS analysis of BrCN degradation products showed that unknown modifications occurred close to both ends of the protein.III. Chromosome segregation and DNA-protein interaction.1. Intracellular localization of a protein involved in chromosome segregation : Human DNA topoisoemrase IIIβ was found to be associated with chromosomes in the M-phase.2. Characterization of a protein interacting with a protein involved in chromosome segregation : The intracellular distribution was examined for the two isoforms of a human DnaH homologue, HSJ2, which had been isolated by two-hybrid screening as human topoisomerase IIIa as bait. The longer gene product was localized to the nucleus, whereas the shorter one was observed uniformly throughout the cell.