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Research has been conducted on LINE-1 retrotransposition. The use of the plasmid-based rescue system in recovering LINE-1 retrotransposition events from the cultured human HeLa cells is described.

Research shows that plasmid DNA contains fully methylated DNA of lowered helical density, which represents a precursor of replication. Furthermore, Lon-protease removes the proteins that lower the helical density during plasmid DNA replicative process.

Research was conducted to characterize a DNA site associated with the chromosome partitioning in Bacillus subtilis. B. subtilis strains that contained the trpC and pheA mutations were derived from AG174 while double crossover technique transformation was utilized to introduce mutations into the chromosome. Results revealed a family of chromosome partitioning sites from B. subtilis and showed that the presence of a single site on stabilized the plasmid.

DNA segregation in E. coli has been investigated by the insertion of multiple lac operator seqeuences into a chromosome near origin of replication, in the hisC gene and P1 and F plasmids. Origin of replication was found to be specifically sited at or near cell poles. P1 and F were sited at the cell center and moved rapidly on duplication.

F plasmid, the fertility factor of E. coli, is partitioned with fidelity to daughter cells during cell division, due to sopA and sopB, trans-acting genes, and sopC, a cis-acting site. The subcellular distribution of mini-F-plasmid molecules was visualized through fluorescence in situ hyrbidization. Molecules lacking the sopABC segment showed random distribution in spaces not occupied by nucleoids.

The authors discuss their research on plasmid toxin-antitoxin systems which kill daughter cells. The topics of interest include the ability of Escherichia coli toxin to cleave mRNA in the ribosomal A site in order to make it function as stress regulator during amino acid starvation.