Affiliation:
1. Center for Molecular Oncology and Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, Illinois
Abstract
ABSTRACT
Temperature-sensitive DNA polymerase mutants (
dnaE
) are protected from cell death on incubation at nonpermissive temperature by mutation in the
cydA
gene controlling cytochrome
bd
oxidase. Protection is observed in complex (Luria-Bertani [LB]) medium but not on minimal medium. The
cydA
mutation protects a thymine-deficient strain from death in the absence of thymine on LB but not on minimal medium. Both
dnaE
and
Δthy
mutants filament under nonpermissive conditions. Filamentation per se is not the cause of cell death, because the
dnaE cydA
double mutant forms long filaments after 24 h of incubation in LB medium at nonpermissive temperature. These filaments have multiply dispersed nucleoids and produce colonies on return to permissive conditions. The protective effect of a deficiency of
cydA
at high temperature is itself suppressed by overexpression of cytochrome
bo3
, indicating that the phenomenon is related to energy metabolism rather than to a specific effect of the
cydA
protein. We propose that filamentation and cell death resulting from thymine deprivation or slowing of DNA synthesis are not sequential events but occur in response to the same or a similar signal which is modulated in complex medium by cytochrome
bd
oxidase. The events which follow inhibition of replication fork progression due to either polymerase inactivation, thymine deprivation, or hydroxyurea inhibition differ in detail from those following actual DNA damage.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
8 articles.
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