Effect of supercoiling on the λ switch

Kamilla Norregaard; Magnus Andersson; Kim Sneppen; Peter Eigil Nielsen; Stanley Brown; Lene B Oddershede

doi:10.4161/bact.27517

Effect of supercoiling on the λ switch

Kamilla Norregaard, Magnus Andersson, Kim Sneppen, Peter Eigil Nielsen, Stanley Brown, Lene B Oddershede

Abstract

The lysogenic state of the λ switch is exceptionally stable, still, it is capable of responding to DNA-damage and rapidly enter the lytic state. We invented an assay where PNA mediated tethering of a plasmid allowed for single molecule investigations of the effect of supercoiling on the efficiency of the epigenetic λ switch. Compared with non-supercoiled DNA, the presence of supercoils enhances the CI-mediated DNA looping probability and renders the transition between the looped and unlooped states steeper, thus increasing the Hill coefficient. Interestingly, the transition occurs exactly at the CI concentration corresponding to the minimum number of CI molecules capable of maintaining the pRM-repressed state. Based on these results we propose that supercoiling maintains the pRM-repressible state as CI concentration decline during induction and thus prevent autoregulation of cI from interfering with induction.

Original language	English
Article number	e27517
Journal	Bacteriophage
Volume	4
Issue number	2
Pages (from-to)	1-5
Number of pages	5
ISSN	2159-7073
DOIs	https://doi.org/10.4161/bact.27517
Publication status	Published - 1 Jan 2014

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title = "Effect of supercoiling on the λ switch",

abstract = "The lysogenic state of the λ switch is exceptionally stable, still, it is capable of responding to DNA-damage and rapidly enter the lytic state. We invented an assay where PNA mediated tethering of a plasmid allowed for single molecule investigations of the effect of supercoiling on the efficiency of the epigenetic λ switch. Compared with non-supercoiled DNA, the presence of supercoils enhances the CI-mediated DNA looping probability and renders the transition between the looped and unlooped states steeper, thus increasing the Hill coefficient. Interestingly, the transition occurs exactly at the CI concentration corresponding to the minimum number of CI molecules capable of maintaining the pRM-repressed state. Based on these results we propose that supercoiling maintains the pRM-repressible state as CI concentration decline during induction and thus prevent autoregulation of cI from interfering with induction.",

author = "Kamilla Norregaard and Magnus Andersson and Kim Sneppen and Nielsen, {Peter Eigil} and Stanley Brown and Oddershede, {Lene B}",

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T1 - Effect of supercoiling on the λ switch

AU - Norregaard, Kamilla

AU - Andersson, Magnus

AU - Sneppen, Kim

AU - Nielsen, Peter Eigil

AU - Brown, Stanley

AU - Oddershede, Lene B

PY - 2014/1/1

Y1 - 2014/1/1

N2 - The lysogenic state of the λ switch is exceptionally stable, still, it is capable of responding to DNA-damage and rapidly enter the lytic state. We invented an assay where PNA mediated tethering of a plasmid allowed for single molecule investigations of the effect of supercoiling on the efficiency of the epigenetic λ switch. Compared with non-supercoiled DNA, the presence of supercoils enhances the CI-mediated DNA looping probability and renders the transition between the looped and unlooped states steeper, thus increasing the Hill coefficient. Interestingly, the transition occurs exactly at the CI concentration corresponding to the minimum number of CI molecules capable of maintaining the pRM-repressed state. Based on these results we propose that supercoiling maintains the pRM-repressible state as CI concentration decline during induction and thus prevent autoregulation of cI from interfering with induction.

AB - The lysogenic state of the λ switch is exceptionally stable, still, it is capable of responding to DNA-damage and rapidly enter the lytic state. We invented an assay where PNA mediated tethering of a plasmid allowed for single molecule investigations of the effect of supercoiling on the efficiency of the epigenetic λ switch. Compared with non-supercoiled DNA, the presence of supercoils enhances the CI-mediated DNA looping probability and renders the transition between the looped and unlooped states steeper, thus increasing the Hill coefficient. Interestingly, the transition occurs exactly at the CI concentration corresponding to the minimum number of CI molecules capable of maintaining the pRM-repressed state. Based on these results we propose that supercoiling maintains the pRM-repressible state as CI concentration decline during induction and thus prevent autoregulation of cI from interfering with induction.

U2 - 10.4161/bact.27517

DO - 10.4161/bact.27517

M3 - Journal article

C2 - 24386605

SN - 2159-7073

VL - 4

SP - 1

EP - 5

JO - Bacteriophage

JF - Bacteriophage

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Effect of supercoiling on the λ switch

Abstract

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