The absence of effect of gid or mioC transcription on the initiation of chromosomal replication in Escherichia coli

The absence of effect of gid or mioC transcription on the initiation of chromosomal replication in Escherichia coli

Departments of ^*Biology and ^§Cell Biology, and ^†Cancer Center, University of New Mexico, Albuquerque, NM 87131; and ^‡Department of Cell Biology, Institute for Cancer Research, Montebello, 0310 Oslo, Norway

Edited by Donald R. Helinski, University of California at San Diego, La Jolla, CA, and approved September 15, 1997 (received for review June 23, 1997)

Abstract

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.

Footnotes

↵ ¶ Present address: Department of Molecular Biology, Wellman 10, Massachusetts General Hospital, Boston MA 02114.
↵ ‖ To whom reprint requests should be addressed. e-mail: kogoma{at}medusa.unm.edu.
This paper was submitted directly (Track II) to the Proceedings Office.
Abbreviations: RNAP, RNA polymerase; IPTG, isopropyl β-d-thiogalactoside.