The AT richness and gid transcription determine the left border of the replication origin of the E. coli chromosome.

摘要: We have identified novel, cis-acting elements which enhance in vivo the replication activity of plasmids carrying minimal oriC Escherichia coli. These are (i) AT rich sequence ('AT-cluster') exists immediately left 13mer repeats and (ii) gid transcriptional unit. The 'AT-cluster' was functionally replaced by an unrelated sequence. This also case for middle 13mers; they were substituted fragment from mini-F plasmid. did not show 'reduced helical stability' known as important character region. In contrast to these results, right strictly required. As effect transcription promoter, activated only when directed away side it. mioC proceeding toward had no on activation. Mutations DnaA boxes partially suppressed leaving side. From we propose that richness is a determinant identify border oriC. It presumed introduces negative superhelicity at region facilitates dependent duplex opening.