groEL and dnaK genes of Escherichia coli are induced by UV irradiation and nalidixic acid in an htpR+-dependent fashion.

Abstract

Two proteins with molecular weights of 61,000 and 73,000 were found to be induced by UV light in Escherichia coli mutants in which the SOS responses are constitutively expressed. The induction of these proteins by UV light and nalidixic acid was shown to be independent of the recA+ lexA + regulatory system. Analysis of these proteins by two-dimensional gel electrophoresis and comparison with the "heatshock" proteins of E. coli revealed that the Mr 61,000 protein comigrated with the groEL gene product, that the Mr 73,000 protein comigrated with the dnaK gene product, and that other heat-shock proteins were also induced. The induction of groEL and dnaK by UV light and nalidixic acid is controlled by the htpR locus. The results suggest that the regulatory response of E. coli to agents such as UV light and nalidixic acid is more complex than previously thought. MATERIALS AND METHODSBacterial strains used are listed in Table 1. Early log cultures grown at 30'C were labeled with [35S]methionine (5 ,uCi/ml, final concentration for one-dimensional gels; 30 ,uCi/ml, final concentration for two-dimensional gels; 1 Ci = 37 GBq) for 5 min and chased for 1 min after various treatments (6). Cell extracts were prepared and the proteins were separated on 10-12% NaDodSO4/polyacrylamide gels as described by Laemmli (10). Two-dimensional gel electrophoresis was carried out as described by O'Farrell (11). Extracts were prepared as for one-dimensional gels and were then diluted 1:3 with sample dilution buffer (12). Fluorographic exposures using Kodak XAR5 film were made of gels treated with EN3HANCE (New England Nuclear).Over the past several years there has been a considerable increase in our understanding of how Escherichia coli responds to DNA damage. Two independent regulatory networks have been identified that are induced by damage to the cell's DNA-the SOS response (1) and the adaptive response (2).Of the two, the adaptive response seems to be the simpler. It is induced by exposure to methylating or ethylating agents but not by agents such as UV irradiation or 4-nitroquinoline-1-oxide (3). Two proteins have been shown to be induced in this response, the 06-methylguanine-DNA methyltransferase and a 3-methyladenine glycosylase (4); the product of the ada gene regulates their induction (4).The SOS response seems to be more complex (1). It is induced by agents and conditions that either damage DNA or interfere with DNA replication. Typical inducing agents are UV irradiation, nalidixic acid, and mitomycin C. The expression of genes in the SOS network is controlled by two regulatory elements, the recA and lexA proteins. The lexA protein serves as the repressor of each of the din (damage-inducible) genes (5) that have been identified to date (1); lexA(Def) mutations that eliminate lexA function cause the high-level constitutive expression of din genes (1, 6). After SOS-inducing treatments, a protease activity of the recA protein is activated that then cleaves the lexA protein leading to the induction of the din genes (1). To...

The Agrobacterium tumefaciens vir gene transcriptional activator virG is transcriptionally induced by acid pH and other stress stimuli

“…3). At least some of these treatments, including those with CdCl2 (57), mitomycin C (25), and alkaline pH (45,56), induce multiple stress regulons in E. coli. In contrast, heat shock and ethanol, which induced virG poorly or not at all, induce only the heat shock proteins in E. coli (57).…”

“…Other forms of cellular stress have been shown to induce the synthesis of some of the heat shock proteins. These include treatment with ethanol, heavy metals (57), DNA-damaging agents (25,57), or extreme pH shifts (16,17,56). Recent work suggests that the A. tumefaciens heat shock response is similar to the E. coli response and that A. tumefaciens has a cr32-like sigma factor (31).…”

Induction of the heat shock response of E. coli through stabilization of sigma 32 by the phage lambda cIII protein.

“…Heat shock proteins are likely to be general contributors to survival from extreme stress (Krueger and Walker 1984;Neidhardt et al 1984); thus, elevated production might help the host survive the viral infection, a helpful event for both host and phage in the lysogenic response favored by cIII. Certain heat shock proteins also participate directly in k development (e.g., DnaJ, DnaK, and GrpE in k replication and GroEL and GroES in morphogenesis) (Friedman et al 1984;Ang et al 1986;Bardwell et al 1986).…”

A grpE mutant of Escherichia coli is more resistant to heat than the wild-type

“…In order to determine if grpE cells are generally resistant to agents which induce the heat-shock response, the wild-type and grpE mutant strains were subjected to H202 and UV treatments, both of which induce the heatshock response in E. coli (VanBogelen et al, 19876; Krueger & Walker, 1984). In addition, H 2 0 2 has been shown to induce thermotolerance in E. coli (VanBogelen et al, 1987a).…”