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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.

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CII levels at heat induction. Strains W3110 (λcI857knR) and A8926 (λcI857knR) were grown overnight in Luria–Bertani at 32°C and then diluted 1:100 into 10 ml minimal media and grown to OD600 of 0.3. The cultures were transferred to 42°C for 10 min and were then returned to 32°C. Samples were taken at the indicated times from the onset of heat. Samples were loaded on 4–12% NuPAGE (Invitrogen), and CII levels were detected by Western blot using antibodies raised against the full-length CII (Kobiler et al., 2002).
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fig03: CII levels at heat induction. Strains W3110 (λcI857knR) and A8926 (λcI857knR) were grown overnight in Luria–Bertani at 32°C and then diluted 1:100 into 10 ml minimal media and grown to OD600 of 0.3. The cultures were transferred to 42°C for 10 min and were then returned to 32°C. Samples were taken at the indicated times from the onset of heat. Samples were loaded on 4–12% NuPAGE (Invitrogen), and CII levels were detected by Western blot using antibodies raised against the full-length CII (Kobiler et al., 2002).

Mentions: Heat treatment of the lysogen for 5 min leads to CII activity as measured by the pE–GFP fusion (Fig. 2A). As detected by Western blot, the CII protein made during the first 5 min at 42°C is eliminated during the next 5 min at 42°C (Fig. 3). This elimination of CII protein explains the lack of CII activity after the 10 or 15 min heat pulse.Fig. 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)

CII levels at heat induction. Strains W3110 (λcI857knR) and A8926 (λcI857knR) were grown overnight in Luria–Bertani at 32°C and then diluted 1:100 into 10 ml minimal media and grown to OD600 of 0.3. The cultures were transferred to 42°C for 10 min and were then returned to 32°C. Samples were taken at the indicated times from the onset of heat. Samples were loaded on 4–12% NuPAGE (Invitrogen), and CII levels were detected by Western blot using antibodies raised against the full-length CII (Kobiler et al., 2002).
© Copyright Policy
Related In: Results  -  Collection

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

fig03: CII levels at heat induction. Strains W3110 (λcI857knR) and A8926 (λcI857knR) were grown overnight in Luria–Bertani at 32°C and then diluted 1:100 into 10 ml minimal media and grown to OD600 of 0.3. The cultures were transferred to 42°C for 10 min and were then returned to 32°C. Samples were taken at the indicated times from the onset of heat. Samples were loaded on 4–12% NuPAGE (Invitrogen), and CII levels were detected by Western blot using antibodies raised against the full-length CII (Kobiler et al., 2002).
Mentions: Heat treatment of the lysogen for 5 min leads to CII activity as measured by the pE–GFP fusion (Fig. 2A). As detected by Western blot, the CII protein made during the first 5 min at 42°C is eliminated during the next 5 min at 42°C (Fig. 3). This elimination of CII protein explains the lack of CII activity after the 10 or 15 min heat pulse.Fig. 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