DNA supercoiling: A regulatory signal for the λ repressor

Condensed Matter journal club

DNA supercoiling: A regulatory signal for the λ repressor

  • Event time: 11:30am
  • Event date: 5th December 2014
  • Location: Room 2511,

Event details

Abstract

Low levels of λ repressor (CI) can autoenhance expression and lysogeny (quiescence) of bacteriophage λ infection. However, additional CI mediates an autorepressive DNA loop. Supercoiling catalyzes looping in unstretched plasmids, but whether supercoiling catalyzes looping under tension, and whether the cI promoter within the loop becomes superhelically isolated were investigated. CI efficiently partitioned plasmids into topological domains and formed barriers to the passage of supercoiling from one into another. Furthermore, in single DNA molecules twisted with magnetic tweezers, CI-mediated DNA loops confined as much as -15% to +11% supercoiling. Finally, under gentle tensions likely to occur in vivo, supercoiling was essential for looping. CI may exploit supercoil-driven looping events to regulate the lysogenic/lytic switch.
PNAS 111 pages 402-15407 (2014)
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Authors

Yue Ding, Carlo Manzo, Geraldine Fulcrand, Fenfei Leng, David Dunlap, Laura Finzi