Two means of transcriptional reactivation within heterochromatin

We describe the cytological analysis of chromatin in ddm1 and mom1 mutants

Aline V. Probst; Paul F. Fransz; Jerzy Paszkowski; Ortrun Mittelsten Scheid


Scholarcy highlights

  • Chromatin of interphase nuclei can be distinguished in decondensed, potentially active euchromatin, and condensed late-replicating heterochromatin with repressed transcription
  • To assess possible global changes in chromatin organization associated with transcriptional gene silencing release by the ddm1 and mom1 mutations, we first examined nuclei of transgenic Arabidopsis line A, the genetic background of the mom1 and ddm1-5 mutant alleles studied here
  • The transcriptional activity of the hygromycin phosphotransferase locus was lost in the progeny of the primary transgenic plant
  • We combined DAPI staining of DNA and fluorescent insitu hybridization with the following probes: pAL1, which labels the core centromeric regions of all chromosomes, transcriptionally silent information specific to pericentromeric repeats, ribosomal DNA, and a telomeric probe
  • As the loss of the MOM1 protein affected neither global organization of heterochromatin nor DNA methylation, we examined particular modifications of histones associated with transcriptional activity or silencing
  • Our studies revealed drastic changes in nuclear organization, DNA methylation, and histone modifications resulting from the ddm1 mutation
  • Nuclear organization in mom1 appears unaltered, demonstrating an involvement of MOM1 in transcriptional regulation within a heterochromatic environment

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