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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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A mutation in the cro gene increases CII activity following heat-shock induction or SOS induction. Cells lysogenic for λcI857cro27 were induced for 10 min under the experimental conditions described and coloured as in Fig. 2 (left). 10 mg ml−1 mitomycin C were added to cells lysogenic for λcI+cro071 and fluorescence levels were then followed at 32°C (right). Fluorescence levels (top) and promoter activity (bottom) are shown.
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fig06: A mutation in the cro gene increases CII activity following heat-shock induction or SOS induction. Cells lysogenic for λcI857cro27 were induced for 10 min under the experimental conditions described and coloured as in Fig. 2 (left). 10 mg ml−1 mitomycin C were added to cells lysogenic for λcI+cro071 and fluorescence levels were then followed at 32°C (right). Fluorescence levels (top) and promoter activity (bottom) are shown.

Mentions: The Cro function reduces transcription from both pR and pL promoters (Fig. 1B). Induction of a prophage carrying a mutation in the cro gene is predicted to lead to higher, continuous transcription of both the cII and the cIII genes. As expected, significant CII function was observed following either heat or mitomycin C induction of a cro- lysogen (Fig. 6). Following mitomycin C induction, the appearance of CII activity is delayed and coincides with Q activity. The results suggest that the absence of CII in cro+ prophages either following prolonged heat treatment or SOS induction could be because there is only a limiting amount of CII made under these stress-induced conditions, and it is rapidly degraded. The increase in CII expression in a cro- mutant overcomes its downregulation and allows CII activity to be measured.


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)

A mutation in the cro gene increases CII activity following heat-shock induction or SOS induction. Cells lysogenic for λcI857cro27 were induced for 10 min under the experimental conditions described and coloured as in Fig. 2 (left). 10 mg ml−1 mitomycin C were added to cells lysogenic for λcI+cro071 and fluorescence levels were then followed at 32°C (right). Fluorescence levels (top) and promoter activity (bottom) are shown.
© Copyright Policy
Related In: Results  -  Collection

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

fig06: A mutation in the cro gene increases CII activity following heat-shock induction or SOS induction. Cells lysogenic for λcI857cro27 were induced for 10 min under the experimental conditions described and coloured as in Fig. 2 (left). 10 mg ml−1 mitomycin C were added to cells lysogenic for λcI+cro071 and fluorescence levels were then followed at 32°C (right). Fluorescence levels (top) and promoter activity (bottom) are shown.
Mentions: The Cro function reduces transcription from both pR and pL promoters (Fig. 1B). Induction of a prophage carrying a mutation in the cro gene is predicted to lead to higher, continuous transcription of both the cII and the cIII genes. As expected, significant CII function was observed following either heat or mitomycin C induction of a cro- lysogen (Fig. 6). Following mitomycin C induction, the appearance of CII activity is delayed and coincides with Q activity. The results suggest that the absence of CII in cro+ prophages either following prolonged heat treatment or SOS induction could be because there is only a limiting amount of CII made under these stress-induced conditions, and it is rapidly degraded. The increase in CII expression in a cro- mutant overcomes its downregulation and allows CII activity to be measured.

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