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SUMMARY:A New Kind of Protein-DNA Interaction in Replication Termination -
  Nick Dixson
DTSTART:20080423T093000Z
DTEND:20080423T103000Z
UID:TALK11082@talks.cam.ac.uk
CONTACT:Giorgio Favrin
DESCRIPTION:Complexes of the Tus replication terminator protein with Ter D
 NA sites in the terminus region of the E. coli chromosome block replicatio
 n forks when they approach from one direction\, but not the other. The fir
 st arriving fork is thus trapped between oppositely oriented Ter sites\, w
 here it stalls\, awaiting the arrival of the second fork [1]. Two\nmechani
 sms have been proposed to explain polarity of action of the Tus-Ter replic
 ation fork block. One involves specific interactions of the replicative Dn
 aB helicase at the fork-blocking (non-permissive) face of the Tus-Ter comp
 lex [2]. The other [3] depends on strand separation by DnaB at the front o
 f the replisome: approach of the replisome from the permissive direction l
 eads to displacement of Tus from Ter\, while approach from the non-permiss
 ive direction results in formation of a remarkably stable "locked" complex
 . "Lock" formation requires a conserved cytosine residue in Ter\, which mo
 ves 14 Å from its normal position to bind in a cytosine-specific pocket o
 n the surface of Tus. The roles of the two mechanisms in determining polar
 ity of action of the Tus-Ter block will be reviewed\, and potential applic
 ations of this tight DNA-protein complex discussed.\n\n[1] Neylon et al. (
 2005) Microbiol. Mol. Biol. Rev.\, 69\, 501-526.\n[2] Mulugu et al. (2001)
  Proc.  Natl.  Acad.  Sci.  USA\, 98\, 9569-9574.\n[3] Mulcair et al. (200
 6) Cell\, 125\, 1309-1319.\n\n
LOCATION:Unilever Lecture Theatre\, Unilever Centre\, Department of Chemis
 try
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