Disease relevance of topB

• Molecular cloning and DNA sequence analysis of Escherichia coli topB, the gene encoding topoisomerase III [1].

High impact information on topB

• DNA topoisomerase III from Escherichia coli belongs to the type IA family of DNA topoisomerases, which transiently cleave ssDNA via formation of a covalent 5' phosphotyrosine intermediate [2].
• The gene encoding Topo III (topB) can be deleted without affecting cell viability [3].
• The polypeptide encoded by the plasmid RP4 traE gene shows extensive protein sequence similarity to Escherichia coli topB, the gene encoding DNA topoisomerase III (Topo III) [4].
• Escherichia coli DNA topoisomerase III is a site-specific DNA binding protein that binds asymmetrically to its cleavage site [5].
• The deduced amino acid sequence of Exc had low amino acid sequence similarity to DNA topoisomerase III, an enzyme that relaxes DNA supercoils [6].

Biological context of topB

• The products of the orf183 and topB genes were required neither for selenoprotein biosynthesis nor for selenation of tRNAs. selAB transcription was driven by a single, weak promoter; however, two major selD operon transcripts were identified [7].
• Frameshift mutations in topB strain also significantly increased compared with those of wild-type (17 vs. 2%) [8].
• The present data suggest that topB is a novel class of mutator that strongly induces repeated sequence dependent deletion mutagenesis and high frequencies of frameshift mutagenesis [8].
• A 17-amino-acid residue domain has been identified in Escherichia coli DNA topoisomerase III (Topo III) that is essential for Topo III-mediated resolution of DNA replication intermediates in vitro [9].

Associations of topB with chemical compounds

• (ii) Mutations in mutR can be induced with the frameshift mutagen ICR-191 [10].

Other interactions of topB

• Isolation of the topB gene encoding DNA topoisomerase III as a multicopy suppressor of topA null mutations in Escherichia coli [11].

References