期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2006
卷号：103
期号：32
页码：12051-12056
DOI：10.1073/pnas.0605120103
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：The bacterium Vibrio cholerae has two chromosomes. The origin of replication of chromosome I is similar to that of Escherichia coli. The origin-containing region of chromosome II (oriCII) resembles replicons of plasmids such as P1, except for the presence of an additional gene, rctA [Egan, E. S. & Waldor, M. K. (2003) Cell 114, 521-530]. The oriCII region that includes the initiator gene, rctB, can function as a plasmid in E. coli. Here we show that RctB suffices for the oriCII-based plasmid replication, and rctA in cis or trans reduces the plasmid copy number, thereby serving as a negative regulator. The inhibitory activity could be overcome by increasing the concentration of RctB, suggesting that rctA titrates the initiator. Purified RctB bound to a DNA fragment carrying rctA, confirming that the two can interact. Although rctA apparently works as a titrating site, it is nonetheless transcribed. We find that the transcription attenuates the inhibitory activity of the gene, presumably by interfering with RctB binding. RctB, in turn, repressed the rctA promoter and, thereby, could control its own titration by modulating the transcription of rctA. This control circuit appears to be a putative novel mechanism for homeostasis of initiator availability.
关键词：checkpoint control ; DNA–protein interactions ; homeostasis ; replication control
