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SUMMARY:The topological equivalence of the yeast chromosome centromere and
  the yeast plasmid partitioning locus - Jayaram\, M (University of Texas a
 t Austin\, USA)
DTSTART:20120903T091000Z
DTEND:20120903T095000Z
UID:TALK39496@talks.cam.ac.uk
CONTACT:Mustapha Amrani
DESCRIPTION:Centromeres are the DNA loci responsible for the faithful part
 itioning of eukaryotic\nchromosomes. The elaborate protein assembly\, call
 ed the kinetochore complex\, organized at the centromere is responsible fo
 r attaching sister chromosomes to the mitotic spindle\, thus ensuring thei
 r equal segregation during cell division. Centromeres in nearly all eukary
 otes are regional centromeres- long DNA segments with no consensus sequenc
 e elements- that are established epigenetically. Members of the budding ye
 ast lineage are a stark exception. Their chromosomes harbor point centrome
 res- very short centromeres with three well defined sequence elements- tha
 t are genetically determined. The yeast centromere chromatin engenders a p
 ositive supercoil\, presumably due to a nucleosome containing a variant of
  the histone H3. Yeast harbors a selfish plasmid whose stability is compar
 able to that of the chromosomes of its host. The plasmid achieves this fid
 elity of segregation with the help of two partitioning proteins and a part
 itioning locus called STB (for stability). Strikingly\, the chromatin at S
 TB is also positively supercoiled. When STB function is inactivated\, its 
 topology shifts to standard negative supercoiling. The magnitudes of the C
 EN and STB induced positive supercoiling are comparable. The topological e
 quivalence of CEN and STB\, along with other functional similarities betwe
 en the two\, are consistent with the notion that the non-standard point ce
 ntromere had its origin in the partitioning locus of an ancestral plasmid.
 \n
LOCATION:Seminar Room 1\, Newton Institute
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