Interplay between Two Epigenetic Marks

Using chromatin immunoprecipitation assays, we show that Arabidopsis heterochromatin is associated with H3-K9 methylation

Lianna M. Johnson; Xiaofeng Cao; Steven E. Jacobsen

2002

Scholarcy highlights

  • Heterochromatic regions of the genome, located primarily in centromeres and telomeres, are generally characterized by increased chromatin condensation and decreased access to regulatory proteins
  • The centromeric repeats serve as excellent loci in which to study the relationship between histone methylation and DNA methylation without the complication of transcriptional effects
  • Cmt3 causes a dramatic loss of DNA methylation and derepresses SUP gene silencing, little loss in H3-K9 methylation is observed. These results suggest that DNA methylation, not H3-K9 methylation, is primarily responsible for gene silencing at SUP
  • We have shown that Arabidopsis heterochromatin is characterized by DNA methylation, and by histone H3-K9 methylation
  • Plants, like animals and fungi, show high levels of H3-K9 methylation in heterochromatin and low levels in euchromatin, and this finding suggests conservation of this phenomenon amongst the major eukaryotic groups. The loss of this methylation in the kyp mutant suggests that the KRYP TONITE lysine 9-specific histone H3 methyltransferase is the major enzyme maintaining H3-K9 methylation at heterochromatin
  • We find that mutation of the SWI2/SNF2-related DDM1 gene is as effective in universally reducing histone H3-K9 methylation as is the kyp mutant
  • This suggests that chromatin remodeling is required for maintenance of DNA methylation, and for the maintenance of histone methylation

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