Induction of only one SOS operon, umuDC, is required for SOS mutagenesis in Escherichia coli |
| |
Authors: | Suzanne Sommer Jelena Knezevic Adriana Bailone and Raymond Devoret |
| |
Institution: | (1) Groupe d'Etude Mutagénèse et Cancérogénèse , Laboratoire d'Enzymologie, CNRS, F-91198 Gif-sur-Yvette, France;(2) Laboratory for Microbiology, Institute of Botany, Faculty of Science, University of Belgrade, 43 Takovska, 11000 Belgrade, Serbia |
| |
Abstract: | The actions of UmuDC and RecA proteins, respectively in SOS mutagenesis are studied here with the following experimental strategy. We used lexAl (Ind–) bacteria to maintain all SOS proteins at their basal concentrations and then selectively increased the concentration of either UmuDC or RecA protein. For this purpose, we isolated operator-constitutive mutations o
c in the umuDC and umuD'C operons and also used the o
98
c
-recA mutation. The o
1
c
-umuDC mutation prevents LexA repressor from binding to the operator and improves the Pribnow box consensus sequence. As a result, 5000 UmuD and 500 UmuC molecules per cell were produced in lexAl bacteria. This concentration is sufficient to restore SOS mutagenesis. The level of RecA protein present in the repressed state promoted full UmuD cleavage. Overproduction of RecA alone did not promote SOS mutagenesis. Increasing the level of RecA in the presence of high concentrations of UmuDC proteins has no further effect on SOS mutgenesis. We conclude that, after DNA damage, umuDC is the only SOS operon that must be induced in Escherichia coli to promote SOS mutagenesis. |
| |
Keywords: | Constitutive operator mutations UmuDC proteins SOS mutagensis LexA repressor binding |
本文献已被 SpringerLink 等数据库收录! |
|