Julius B. Lucks/Bibliography/Gottesman-MicrobiolMolBiolRev-68-2004

Notes on [1]

• review of history of discovery of lambda - what it was used for in the field
• establishment of repression and prophage insertion are distinct steps in establlishment of lysogeny

Prophage Insertion

• Cambell mechanism - 1968 review (28) - Fig 1
  • also (24,31)
  • Hershey - cohesive ends making ring (91) - also (207)
    • DNA ligase helps ring closure - Gellert (68)
  • phage-encoded site-specific recombinase (178,179)
    • see also (87,138) for attP-attB recombination rules - site-specificity gives high efficiency and does not require extensive homology
• (118) - 15 bp region where recombination occurs - see also 200
• Guerrini (87) - prophage excision not simple chemical reversal of prophage insertion
  • lambbda mutants unable to excise (84)
    • (49) - diff conditions for favoring integration over excision and vice versa
    • integrase more stable than Xis (201)
  • Xis produced from P_L, Int produced from P_Int
    • P_Int activated by CII - CII coordinates Int synthesis and repressor synthesis (35)
  • after induction, both Int and Xis produced from P_L
    • (49,83) - Guarneros and Court - how Int produced from both P_L and P_Int - Fig 2
      • sib - sit of endonucleolytic RNase cleavage - promoter distal to int
      • N - suppresses termination of certain phage transcripts
• P_L transcripts contain sib because termination suppressed by N - therefore cleaved and destabilizes int message
  • P_L transcript made after induction does not contain sib b.c. of gene permutation after inserts (Fig 1)
• P_Int transcripts terminate before sib and are more stable (173,174)
  • start site is within xis
  • terminate at T_Int, and do not contain complete sib
• excision requires Int and Xis
  • in vitro integration/excision - (77,148,149)
• Int a type I topoisomerase (115)
• IHF (host integration factor) required for integration (150,151)
  • 2 subunits - ihfA (hid/himA), and ihfB (hip/himD) (114,136,204)
  • architectural role - bends DNA to form Int-attP-IHF intasome (73)
• effective integration requires negative supercoils (69,139)

References

1. Gottesman ME and Weisberg RA. Little lambda, who made thee?. Microbiol Mol Biol Rev. 2004 Dec;68(4):796-813. DOI:10.1128/MMBR.68.4.796-813.2004 |

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