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

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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.