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DTSTART:20250330T030000
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BEGIN:VEVENT
DTSTAMP:20260312T163653Z
UID:1761121800@ist.ac.at
DTSTART:20251022T103000
DTEND:20251022T113000
DESCRIPTION:Speaker: Maike Stam\nhosted by Xiaoqi Feng\nAbstract: Paramutat
 ion\, the transfer of heritable silencing information between two homologo
 us alleles\, results in the silencing of a susceptible allele (1\,2). Para
 mutation requires multiple components of the RNA-directed DNA methylation 
 (RdDM) pathway\, which is characterized by 24nt siRNAs and CHH methylation
  (H=A\,T\, or C). With paramutation at the maize b1 gene\, affecting plant
  pigmentation\, the low expressed\, inducing B’ epiallele heritably chan
 ges the high expressed\, sensitive B-I epiallele into B’ with 100% frequ
 ency. A hepta-repeat 100kb upstream of the b1 gene is required for paramut
 ation and high b1 expression (3). High B-I expression correlates with hist
 one acetylation\, nucleosome depletion\, and a multi-loop chromatin struct
 ure at the b1 locus\, whereas low B’ expression correlates with DNA hype
 rmethylation\, the repressive histone modifications H3K9me2\, H3K27me2\, a
 nd a single-loop chromatin structure (4-6). However\, surprisingly\, param
 utation at the b1 locus appears associated with more RdDM activity at the 
 sensitive allele than at the inducing allele. I will discuss the hypothesi
 s why this may be in the seminar. I will furthermore discuss results obtai
 ned with mutants in the RdDM pathway that indicate a role for RdDM compone
 nts in maintaining H3K9me2 and H3K27me2 independent of their role in estab
 lishing DNA methylation (6). References:1. Hövel et al. (2015) Sem. Cell
  & Dev. Biol. doi: 10.1016/j.semcdb.2015.08.012.2. Hollick (2017) Nat Rev.
  Genetics doi: 10.1038/nrg.2016.115.3. Stam et al. (2002) Genes & Dev doi:
  10.1101/gad.1006702.4. Haring et al. (2010) Plant J. doi: 10.1111/j.1365-
 313X.2010.04245.x 5. Louwers et al (2009) Plant Cell\, doi/10.1105/tpc.10
 8.064329 6. Hövel et al. (2024) Plant Physiology\, doi: 10.1093/plphys/k
 iae072.
LOCATION:Office Bldg West / Ground floor / Foyer seminar room\, ISTA
ORGANIZER:
SUMMARY:Maike Stam: Heritable in trans silencing at the maize b1 locus: a s
 tory about distal cis-regulatory sequences\, RNA-directed DNA methylation 
 and unexpected epigenetic profiles.
URL:https://talks-calendar.ista.ac.at/events/6059
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