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SUMMARY:*ectopic seminar* Evidence for the existence of organism-specific 
 regulatory elements that are linked to RNAi - Isidore Rigoutsos\, IBM T.J.
  Watson Research Center\, Yorktown Heights\, U.S.A.
DTSTART:20061031T150000Z
DTEND:20061031T160000Z
UID:TALK5716@talks.cam.ac.uk
CONTACT:Gos Micklem
DESCRIPTION:In this presentation\, I will describe results from our analys
 es of the intergenic and intronic regions of several genomes. Working with
  the human genome\, we identified large numbers of statistically significa
 nt\, distinct\, variable-length motifs in its intergenic and intronic regi
 ons with intact copies that total in the millions. A subset of more than o
 ne hundred thousand of these conserved motifs\, which we termed 'pyknons' 
 have several hundred thousand instances in the untranslated and coding reg
 ions of more than 90% of all known human genes\, in addition to their nume
 rous human intergenic and intronic copies. Additional analysis showed that
  pyknons are enriched in a statistically significant manner in genes invol
 ved in specific processes\, e.g. cell communication\, transcription\, regu
 lation of transcription\, signaling\, transport\, etc. Cross-genome compar
 isons revealed that many human pyknons have instances in the 3'UTRs of gen
 es from other vertebrates and invertebrates where they are overrepresented
  in similar biological processes\, as in the human genome. We also obtaine
 d analogous results from our analyses of a number of other genomes. In fac
 t\, we found that pyknon collections exist in vertebrates and invertebrate
 s\, and that they exhibit similar properties. A notable observation is tha
 t pyknon collections from different genomes have generally little overlap 
 suggesting that these motifs are organism-specific. I will also discuss re
 cent experimental evidence from several genomes that provides support to t
 he hypothesis that pyknons indeed correspond to active molecules with regu
 latory role and that they are linked with RNAi. The sheer number of pyknon
 s in a given organism suggests the existence of a very broad\, endogenous 
 layer of organization and cellular process regulation that remains largely
  uncharacterized.\n
LOCATION:Part II Room\, Department of Genetics
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