Limits...
Host responses influence on the induction of lambda prophage.

Rokney A, Kobiler O, Amir A, Court DL, Stavans J, Adhya S, Oppenheim AB - Mol. Microbiol. (2008)

Bottom Line: We studied the effects of these two methods of induction on the lytic pathway by monitoring the activation of different lambda promoters, and found that the lambda genetic network co-ordinates information from the host stress response networks.Our results show that the function of the CII transcriptional activator, which facilitates the lysogenic developmental pathway, is not observed following either method of induction.We also show that, despite the common inhibitory effect on CII function, there are significant differences in the heat- and SOS-induced pathways leading to the lytic cascade.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Genetics and Biotechnology, The Hebrew University-Hadassah Medical School, Jerusalem, Israel. assafr@ekmd.huji.ac.il

ABSTRACT
Inactivation of bacteriophage lambda CI repressor leads almost exclusively to lytic development. Prophage induction can be initiated either by DNA damage or by heat treatment of a temperature-sensitive repressor. These two treatments also cause a concurrent activation of either the host SOS or heat-shock stress responses respectively. We studied the effects of these two methods of induction on the lytic pathway by monitoring the activation of different lambda promoters, and found that the lambda genetic network co-ordinates information from the host stress response networks. Our results show that the function of the CII transcriptional activator, which facilitates the lysogenic developmental pathway, is not observed following either method of induction. Mutations in the cro gene restore the CII function irrespective of the induction method. Deletion of the heat-shock protease gene ftsH can also restore CII function following heat induction but not following SOS induction. Our findings highlight the importance of the elimination of CII function during induction as a way to ensure an efficient lytic outcome. We also show that, despite the common inhibitory effect on CII function, there are significant differences in the heat- and SOS-induced pathways leading to the lytic cascade.

Show MeSH

Related in: MedlinePlus

Induction of lysogenic cells by UV irradiation or by mitomycin C. Strains W3110 (λc+knR) carrying the pR-gfp (orange), the pE-gfp (blue) or the pR′-tR′-gfp (red) plasmids were irradiated with increasing UV doses (1, 5, 7.5, 10 and 20 J m−2), and GFP expression was followed at 32°C (top). Identical experiments were carried out following addition of mitomycin C at the concentration of 0.1, 1 and 10 mg ml−1, and fluorescence levels were then followed at 37°C (bottom). Light to darker colours represent increasing inducing doses.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2327240&req=5

fig04: Induction of lysogenic cells by UV irradiation or by mitomycin C. Strains W3110 (λc+knR) carrying the pR-gfp (orange), the pE-gfp (blue) or the pR′-tR′-gfp (red) plasmids were irradiated with increasing UV doses (1, 5, 7.5, 10 and 20 J m−2), and GFP expression was followed at 32°C (top). Identical experiments were carried out following addition of mitomycin C at the concentration of 0.1, 1 and 10 mg ml−1, and fluorescence levels were then followed at 37°C (bottom). Light to darker colours represent increasing inducing doses.

Mentions: Lysogenic cells can be induced by DNA-damaging treatments such as UV irradiation or mitomycin C; both treatments lead to activation of the SOS response (Sassanfar and Roberts, 1990). In order to investigate the phage response following SOS induction, lysogenic cells carrying the wild-type prophage were induced with increasing doses of UV or mitomycin C (Fig. 4). The results show that higher levels of GFP expression from the pR and the pR′-tR′ reporters are obtained with increasing UV doses or higher mitomycin C concentrations. We have recently shown in single cell analysis that pR at low UV levels is activated in the majority of the induced cells (Amir et al., 2007). On the other hand, these conditions lead to activation of the pR′-tR′ only in a fraction of the cells, in which pR activity is significantly lower. Interestingly, no expression from the pE promoter was observed at any of the inducing doses (Fig. 4). Similarly, no CII protein was detected by Western blot analysis (not shown). This is in contrast to heat induction, where CII activity was detected after short (5 min) heat treatment (Figs 2B and 3).


Host responses influence on the induction of lambda prophage.

Rokney A, Kobiler O, Amir A, Court DL, Stavans J, Adhya S, Oppenheim AB - Mol. Microbiol. (2008)

Induction of lysogenic cells by UV irradiation or by mitomycin C. Strains W3110 (λc+knR) carrying the pR-gfp (orange), the pE-gfp (blue) or the pR′-tR′-gfp (red) plasmids were irradiated with increasing UV doses (1, 5, 7.5, 10 and 20 J m−2), and GFP expression was followed at 32°C (top). Identical experiments were carried out following addition of mitomycin C at the concentration of 0.1, 1 and 10 mg ml−1, and fluorescence levels were then followed at 37°C (bottom). Light to darker colours represent increasing inducing doses.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2327240&req=5

fig04: Induction of lysogenic cells by UV irradiation or by mitomycin C. Strains W3110 (λc+knR) carrying the pR-gfp (orange), the pE-gfp (blue) or the pR′-tR′-gfp (red) plasmids were irradiated with increasing UV doses (1, 5, 7.5, 10 and 20 J m−2), and GFP expression was followed at 32°C (top). Identical experiments were carried out following addition of mitomycin C at the concentration of 0.1, 1 and 10 mg ml−1, and fluorescence levels were then followed at 37°C (bottom). Light to darker colours represent increasing inducing doses.
Mentions: Lysogenic cells can be induced by DNA-damaging treatments such as UV irradiation or mitomycin C; both treatments lead to activation of the SOS response (Sassanfar and Roberts, 1990). In order to investigate the phage response following SOS induction, lysogenic cells carrying the wild-type prophage were induced with increasing doses of UV or mitomycin C (Fig. 4). The results show that higher levels of GFP expression from the pR and the pR′-tR′ reporters are obtained with increasing UV doses or higher mitomycin C concentrations. We have recently shown in single cell analysis that pR at low UV levels is activated in the majority of the induced cells (Amir et al., 2007). On the other hand, these conditions lead to activation of the pR′-tR′ only in a fraction of the cells, in which pR activity is significantly lower. Interestingly, no expression from the pE promoter was observed at any of the inducing doses (Fig. 4). Similarly, no CII protein was detected by Western blot analysis (not shown). This is in contrast to heat induction, where CII activity was detected after short (5 min) heat treatment (Figs 2B and 3).

Bottom Line: We studied the effects of these two methods of induction on the lytic pathway by monitoring the activation of different lambda promoters, and found that the lambda genetic network co-ordinates information from the host stress response networks.Our results show that the function of the CII transcriptional activator, which facilitates the lysogenic developmental pathway, is not observed following either method of induction.We also show that, despite the common inhibitory effect on CII function, there are significant differences in the heat- and SOS-induced pathways leading to the lytic cascade.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Genetics and Biotechnology, The Hebrew University-Hadassah Medical School, Jerusalem, Israel. assafr@ekmd.huji.ac.il

ABSTRACT
Inactivation of bacteriophage lambda CI repressor leads almost exclusively to lytic development. Prophage induction can be initiated either by DNA damage or by heat treatment of a temperature-sensitive repressor. These two treatments also cause a concurrent activation of either the host SOS or heat-shock stress responses respectively. We studied the effects of these two methods of induction on the lytic pathway by monitoring the activation of different lambda promoters, and found that the lambda genetic network co-ordinates information from the host stress response networks. Our results show that the function of the CII transcriptional activator, which facilitates the lysogenic developmental pathway, is not observed following either method of induction. Mutations in the cro gene restore the CII function irrespective of the induction method. Deletion of the heat-shock protease gene ftsH can also restore CII function following heat induction but not following SOS induction. Our findings highlight the importance of the elimination of CII function during induction as a way to ensure an efficient lytic outcome. We also show that, despite the common inhibitory effect on CII function, there are significant differences in the heat- and SOS-induced pathways leading to the lytic cascade.

Show MeSH
Related in: MedlinePlus