Bates D B, Boye E, Asai T, Kogoma T
Department of Biology, University of New Mexico, Albuquerque, NM 87131, USA.
Proc Natl Acad Sci U S A. 1997 Nov 11;94(23):12497-502. doi: 10.1073/pnas.94.23.12497.
Despite the widely accepted view that transcription of gid and mioC is required for efficient initiation of cloned oriC, we show that these transcriptions have very little effect on initiation of chromosome replication at wild-type chromosomal oriC. Furthermore, neither gid nor mioC transcription is required in cells deficient in the histone-like proteins Fis or IHF. However, oriC that is sufficiently impaired for initiation by deletion of DnaA box R4 requires transcription of at least one of these genes. We conclude that transcription of mioC and especially gid is needed to activate oriC only under suboptimal conditions. We suggest that either the rifampicin-sensitive step of initiation is some other transcription occurring from promoter(s) within oriC, or the original inference of transcriptional activation derived from the rifampicin experiments is incorrect.
尽管普遍认为gid和mioC的转录是克隆oriC高效起始所必需的，但我们发现这些转录对野生型染色体oriC处的染色体复制起始影响很小。此外，在缺乏类组蛋白Fis或IHF的细胞中，gid和mioC的转录都不是必需的。然而，由于缺失DnaA框R4而起始能力严重受损的oriC需要这些基因中的至少一个进行转录。我们得出结论，仅在次优条件下才需要mioC尤其是gid的转录来激活oriC。我们认为，要么起始的利福平敏感步骤是oriC内启动子发生的其他转录，要么从利福平实验得出的转录激活的原始推断是错误的。
