Temperature-Sensitive Initiation of Chromosome Replication in a Mutant of Escherichia coli

Abstract

The properties of Escherichia coli mutant D2-47LT indicate that it is temperaturesensitive for a protein required for the initiation of chromosome replication. The results of several different experiments are consistent with this hypothesis, and no support was found for the alternate hypotheses tested. Although the strain is usually unable to initiate replication at 42 C, some of the initiation proteins are apparently synthesized at the restrictive temperature. This can cause initiation on partially replicated, but not completed, chromosomes. It appears that the temperature-sensitive protein is required for initiation on completed chromosomes.

Initiation of Deoxyribonucleic Acid Replication in a Temperature-Sensitive Mutant of B. subtilis : Evidence for a Transcriptional Step

“…The mutant Ts37 (15) has properties similar to some of the initiation mutants described in E. coli (1,2,9,11,23,30). When a culture exponentially growing at 30 C is shifted to 45 C, DNA synthesis continues for about 30 min and stops, permitting a DNA increase of 40 to 50%.…”

Temperature-Sensitive Initiation of Chromosome Replication in a Mutant of Bacillus subtilis

“…Thus, the control of the initiation of replication appears to play a fundamental role in the regulation of DNA synthesis, although the features of this control are still not clearly understood.The use of mutants altered in the process of initiation of replication at high temperature should allow a better understanding of the regulatory mechanisms concerned. Many laboratories have obtained mutants in which DNA synthesis is blocked at elevated temperature and some of these organisms appear to carry mutations affecting the initiation process (3,7,11,12,18). This paper describes the properties of a mutant of Bacillus subtilis that is temperature sensitive for the initiation of replication.MATERIALS AND METHODS Bacterial strains.…”

Inititation and termination of chromosome replication in Escherichia coli subjected to amino acid starvation

“…One would predict that, when PC2 is starved for leucine and primed for replication in the absence of thymine at 280C, sufficient replication will have occurred within the origin region during the priming step to allow replication of the chromosome to proceed despite a shift of the culture of 400C before readdition of exogenous one or both parental DNA strands at oriC before initiation is blocked since the EcoRI and HindIIIfragments we have examined are relatively large, measuring from When temperature-sensitive mutants in the dnaA and dnaC genes were first isolated, one criterion for their classification as initiation mutants was the inability to initiate replication when cells that had been starved for an amino acid at the permissive temperature were shifted to the nonpermissive temperature before restoration of the amino acid (1,4,8,10). This property could be taken as evidence for a step in initiation which is sensitive to amino acid star- EcoRI fragments from: (a and b) E. coli PC2 syn-acid starvation could simply prevent the accuchronized by temperature shift and labeled with mulation of sufficient dnaA or dnaC protein for [3H]thymidine for 1.5 min (a) or 6 min (b) at the start initiation.…”