RESUMO
The components for termination of DNA replication in Escherichia coli include the terminator signals T1 and T2 and the trans-acting gene tus. We have shown previously that tus maps in a 4-kilobase region of the chromosomal terminus near T2. Through the use of deletion and insertion mutants, the location of the tus gene has now been precisely identified. We sequenced 2416 nucleotides in this region and identified a 927-base-pair open reading frame which encodes Tus. Insertion of a kanamycin-resistance gene in this open reading frame abolished tus activity. We also demonstrated that crude extracts of tus+ cells contain a protein which binds to the T2 terminator sequence.
Assuntos
Proteínas de Bactérias/genética , Replicação do DNA , Proteínas de Ligação a DNA/genética , Proteínas de Escherichia coli , Escherichia coli/genética , Genes Bacterianos , Genes Reguladores , Genes , Regiões Terminadoras Genéticas , Sequência de Aminoácidos , Sequência de Bases , Teste de Complementação Genética , Genótipo , Dados de Sequência Molecular , Plasmídeos , Mapeamento por RestriçãoRESUMO
The terminus region of the E. coli chromosome contains two loci, T1 and T2, that inhibit the progress of replication forks and require the trans-acting factor tus. We have identified a 23 bp terminator signal at T1 and T2 that is within 100 bp of the sites of replication arrest. When an oligodeoxyribonucleotide containing the terminator signal was inserted into a plasmid, replication was halted only in a tus+ strain and when the terminator signal was oriented properly. We also found this terminator sequence in the terminus region of the plasmid R6K and in the origin region of RepFIIA class plasmids. In addition, we found striking similarities between the E. coli terminator signal and the terminator sequence of B. subtilis.